Well might just as well have a mini review here. (Pokemon Y btw, I can't afford both)
I just love how they handle the presentation of the game. Every features is pretty much given to you from the start and you will have a lot of time playing with all kind of novelties. The focus of the game is obviously the new hardware and the new features that the 3DS can do. The story was reduced significantly , though, to be point to be just basically transparent and just there to be there basically. That's fine however, as 1, like I said, the focus is the new features and 2, it is honestly hard to top Black2/White2 and it's better to lower the bar than go all out. There is also a ridiculous amount of though back to previous game, with all kind of references. Speaking of which, Genwunners would love these games, not only because of the Kanto starters, but also because of the majority of the Pokemon encountered are from the first two generations.
The game also encourage competitive play more than ever before, with seriously easy and convenient online features. EVs training can now be done within less than an hour time due to Super Training, IVs breeding is also much easier thanks to Friend Safari.
Only 1 downside though, is that the majority of the first 3D Pokemon game on a machine that support stereoscopic 3D ... is played in 2D. I don't have a 3DSXL so I don't know if there is any different, but on the original 3DS, the 3D led is only lit during battle and selected places, which is a shame since you can't Kalos, without a doubt the most beautiful region yet in 3D. And most of the time, 3D seriously lower the performance of the 3DS, causing the framerate to go down significantly.
In conclusion, do you seriously care? You are obviously going to buy at least 1 copy, everyone with a 3DS is going to buy it, there is no stoping the power of POKEMON!
What I can say though, is get Y. Y get better Megastones and Tyranitar, and while it is ridiculously hard to find Tyranitarite, it's much easier to get other Pokemon than Megastones.
And Mega Charizard Y is much better. It has Drough, which is pretty much the same as having 1/2x resistance to water, and it also have a boost for Fire moves and faster Solar Beam. It also has higher SpA (lower Atk though) which actually give it a role.