Wow that was a really informative post!I think it depends on what you want to use it for and your lifestyle and of course which style of e/w you're considering vs. which style of medium flap. Btw - they're actually the same size in length. Hold the bottom of the two together and you'll see they're the same. The size difference is only in the height.
The pricing definitely differs though. The pre-increase price of a caviar e/w I believe is $1350 USD(or it could be $1395 can't remember exactly) and the pre-increase price of a caviar medium classic flap is $1995USD. As of Nov 1st latest they'll be more expensive.
The e/w typically only has a single chain and there is no double flap. The bijoux chain is a double chain. It also has no back exterior pocket or front pocket. As such there's less nooks & crannies for organization, but really unless you're using those spots to hold papers/cards and can't imagine not having that organizational flexibility you won't miss those pockets. If you only put one layer of items into your flap then the e/w and caviar medium flap really pretty much holds the exact same amount of items. If anything I find it easier to fit slightly more into the e/w or at least have less tight a fit due to the fact that the sides of the e/w can be 100% expanded meaning the sides are 90 degrees perpendicular to the front/back. Whereas the back of the side of the medium flap is actually stitched to the back so you lose a bit of room on both sides.
If you're only going to have one flap ever I'd go with the medium classic flap just cuz it's eternally classic.
After I got my first medium classic flap I got an e/w to diversify a bit and I LOVE it to bits. Really really it. It's easy to get in and out of - I don't have to worry about the inner flap. The one I got has the bijoux chain so it gives me the flexibility to wear it messenger style. The bag is also incredibly light.
If at all possible - I'd go to a dept store or boutique and try out the different styles in the different leather. Sometimes you just gotta rely on that gut feeling and see what you totally fall in love with.
As for colour - if you want anything remotely light coloured I'd stick with caviar. I loooove the feel of the lambskin but so far have only dared to get it in black.
Anyways, hope this was helpful and good luck with your choice!
I guess the E/W just looks longer because proportionally it's shorter so ... ya. did that make sense?