Thanks everyone for valuable and detailed inputs; just realized I have so much to learn reading all your views :) @buettner I agree with you, will lean towards U50 given I already got quite a few of those classic sports watches.
For me, Sinn was just one of those watches that got stuck in my mind and when I finally saw one in flesh (particularly U50 although it wears much smaller than its specs but still good for my wrist; wish it were an inch bigger); I knew I loved it. It will kind of stands out in my collection - speedy would kind of blend in with other watches but Sinn would surely wont get lost in the crowd. Having said that, Speedy is just so cool w that domed, Hesalite crystal. I cant stop myself walking into Omega showrooms to take a look at them like a kid at a candy store (btw, that's the only "modern" Omega I fancy; although I love my vintage Omegas)
Knowing myself, I know I would end up buying both in next few months but first, will get the U50. Aah... my wife is going to be so very pissed at this :P
Thanks again to all; definitely, learnt so much more today.