I own a BB58 Black and I am always in awe of it - in fact, I chose it over a no date submariner that I had access to purchasing, albeit used. Tudor will never disappoint you in quality, accuracy and fit and finish - no doubt. Having said that.
I had been wanting a smaller "everyday" or "Gada" watch, and was perfectly happy to buy a BB36 after convincing myself it wasn't stupid to have two Black Bays - so I trotted off to my AD to start the process. Like you, I happened to see the Longines box and took a peek in. I was totally floored by the Spirit line. I tried on the BB36 and immediately strapped on the Spirit 37 and the difference was night and day. The BB36 felt really flat after wearing the Spirit.
Long story short - I left with the Spirit 37 and I absolutely love it. A little different than comparing a BBGMT and the Zulu Time - but the idea is the same, Longines is killing it.