All of a sudden, I started paying attention to the pochette metis around September. I went through all the questions you had about which one to get. Here are my two cents.
Monogram is understated, and very casual, goes with pretty much everything in the wardrobe. But you do have to worry about vachetta over time. And the fact that it is all over the place. Too much visibility.
The reverse is so hip. I do like it on some girls. But to me, it is still a 2 colored bag so it might not work so well with prints, florals, or super bright colors. But if you wear lots of neutrals, go for the reverse. In the resale market the reverse fetches the most money, to me it has the most return on investment.
For a few hundred dollars more, you get to own the empreinte. The true question here is which color to get? Hello? That's even more headache. I loved the red (cerise). It's the only color that really called out to me, but wearing a red bag requires too much coordination and time which I simply don't have.
In all seriousness, only you can decide. But if so many girls are asking themselves this same question, then Louis Vuitton has done a tremendous job because it means they are all equally beautiful bags.