Which of these Omegas would you choose? Why?

I'd choose the AT based on it having a date, and being the most "everyday casual" of the three. After the AT I'd pick the Railmaster, since my only "issue" with it is the lack of a date. 

Railmaster. Not a fan of the He valve on the PO and I prefer the dateless dial layout of the Railmaster.

Aqua Terra, has the best dial and is the most versatile

I chose that exact Planet Ocean (I was able to get it used, mint condition, with box & papers for under $4,500)

The 39.5 isn't ridiculously thick, but it is a bit heavy for a daily driver in my opinion.  Fortunately, the bracelet is fantastic, otherwise the weight would be a big problem.

Omega did a really nice job of scaling down the PO, a lot of sub-40mm divers look incorrectly proportioned.

My birth year watches. One of each please. Narrowing it down to one I'll take the Railmaster. Omega can try too hard with the styling, imo. I'll take the simplest

Railmaster - this is the exact conversation I had with a colleague of mine a few weeks ago. I think the Railmaster is the most versatile of the three, and I like the simplicity of the dial. Gubbins inside is more or less the same at that price point, all impressive. He bought the new 300 though, so option 4.

Railmaster all the way.

Planet Ocean - I tried on both PO and AT at boutique, although a bit thicker, the PO wears smaller, it hugs the wrist really well. But I would avoid buying the PO with MSRP. 

One thing to add, the AT is actually a real GMT watch, with independent adjustable hour hand, which is a plus if travel a lot.  

Railmaster has the most timeless design, IMO.

I've owned the PO 8500 and the Railmaster (grey dial)

Have not owned the AT as I'm not a PCL guy (but that's subjective) That's not to say its not a looker as it certainly is.....maybe on leather I would vote AT.

speaking of subjective, the P.O. is too top heavy for me. Not that it was too thick, it just didn't sit right with me...YMMV. While it was great to look at, it was not fun to wear....the idea of owning the P.O. was great than actually owning and living with it.

The Railmaster is the winner of this group and was a great fit on my wrist and I loved the dial.....dates are something I can live with or live without and really are based on the dial / markers and how it all works together...or not. It was accurate and versatile and a joy to wear.

I'd choose the Planet Ocean. First of all - on account of the colour. If the black one's the one you're after, it's the most versatile colour-wise. Then there's the bracelet, with a way more adjustable clasp than on the AT or Railmaster. I somehow am not that much of a fan of the denim dial on the Railmaster, and the AT's design lost me when they switched from fine vertical teak pattern to this horizontal one - it reminds me of 1990s trailers and camper vans more than it does of a ship's teak deck.

Keep in mind this - ultimately, each and every one here or elsewhere, me included, will make a recommendation based on personal preferences and pet peeves. And what matters here is which watch do you really feel is most "you."

When I was looking for a modern Longines, I had a LOT of second thoughts every time I thought my mind's made up. HydroConquest 41mm ceramic bezel, Avigation BigEye Chrono, Legend Diver, Heritage Silver Arrow... My horological friends haven't had a moment of rest, I was asking for aesthetic opinions of everyone I could ask. Made polls on Insta. Ultimately, I was talked into going the emotional connection route and went with the Spirit. I have no regrets here.

Yeah, the cal.8500 and now 8900 in the AT have that function, but as opposed to the 8800 in the 39.5mm PO, it does not have a date quickset. Gotta turn the hour hand two times around the dial to advance it by one day. Which isn't exactly much more practical than 1960s semi-quicksets by changing 21-24h.

Whichever one you choose, I'd say that you have very good taste and are a classy gentleman.  👍

• I agree 100% with you about concern with regard to the PO's weight and thickness.  If you got a thick wrist, you can pull it off; otherwise, for people like me, the struggle is real.  I ended up getting the PO in titanium to deal with the weight, but it's still thick.  But, you know, Daniel Craig wore the PO in Casino Royale...  which is, to my mind, the best Bond film of all time!
• AT is an awesome all-around watch.  A couple of things to note:  On the plus side, the AT is super sophisticated looking, and the faceting on the applied indices is absolutely gorgeous.  On the negative side, all that polishing on the case, the bezel, and the center links on the bracelet makes for a giant scuff and scratch magnet.  I tend not to baby my watches at all, so it doesn't bug me at all if I smash my watch into the doorframe, I'll do yard work and heavy lifting with my watches on, etc., etc., but if scuffs and marks will drive your OCD crazy, then beware!
• I've not had any experience with the Railmaster, but in many ways it's very similar to the Seamaster 300 which I do have experience with.  The Railmaster is thinner than the AT, at 12.65mm versus the 13.5mm of the AT.  All the brushed surfaces will better hide scuffs and scratches.  And that dial design is MEGA!

I guess it all boils down to what purpose will the watch primarily serve for you?

If, like me, your "Secret Life of Walter Mitty" includes pretending to be James Bond, then definitely the PO.  If you got lots of yachting around Martha's Vinyard and clam bakes with the Kennedys, then AT.  The Railmaster?  The Railmaster really stand out as pretty unique to me.  It's got this amazing vintage vibe... has this tiny bit of art deco-ness(?) about it.  The cross-hair dial gives it a touch of class, while that deeply brushed grained look on the dial absolutely looks the business, and takes it back into vintage tool watch territory.

If I had to choose between the 3 watches myself, I would choose the Railmaster.  But, maybe only because I don't have one, and the grass is always greener on the other side?

My vote goes to the Aqua Terra, mainly for design and versatility. For me, the AT looks more luxurious than the Railmaster. However, all three are great choices!

My vote goes to the Railmaster- love that dial 

I do have the Railmaster and it is a fantastic under the radar watch. I would consider how important applied indices are. The dial is flat but has lots of character.

The rail master if you plan to wear it on the bracelet. However i LOVE the AT rubber strap. The strap alone sold me personally. 

Aqua Terra if you need a rubber bracelet or date window. Sporty all over yet classy.

Railmaster if you like understatement like zero polish, no applied indices, simple hands. Sporty under the hood yet quiet.

Planet Ocean if your philosophy on divers is, "Big but not quite a Ploprof or Panerai." Sporty and loud.

Don't forget wrist size. Better try it on before committing.

Railmaster. The dial is very pleasing to the eye. Railmasters are totally underrated. What makes it even more annoying is that Omega decided to categorise Railmaster UNDER Seamaster, when they should be like 2 distinct genealogy in the past! I guess for the noobs if it is not called a Seamaster, no one would know what a railmaster is, so they decided to lump railmaster under seamaster, doing such a great disservice to the history and technical innovations of the railmaster!

Thanks for all the comments and opinions. You all gave me some new perspectives to consider. 

Hopefully I’ll be able to make my way to an AD to see these in person at some point. That would make this much easier. 

Railmaster, because it has the most retro vibe.

I am biased, but I would go for the Planet Ocean:

Second the Aqua Terra as it is a beautiful watch.

I am really surprised the Railmaster gets so much support. While I love the original Railmaster design, I think I would get tired of the current denim(?) dial very quickly…

My choice would definitely be for the Railmaster. In fact Im might just have to check one out for myself now.

A good group. I have the AT and am very happy with it. It has the black rubber strap which is incredibly comfortable and good looking. The case can scratch and show wear, I’m ok with that. If that works for you, it can be a good daily wear choice. 

Couldn't agree more. I have my AT on the OEM rubber strap and I can't see myself ever changing that out unless I want to dress the watch up a bit more by putting it on an alligator strap or something like that. But for everyday wear, the rubber is perfect. Comfortable, classy looking. From afar you can't tell it's rubber so it pulls off the dressy but sporty thing easily.