Yeah that's really all it is. If you want a larger screen, go with the X, if you want a smaller, more easily pocketable phone, go with the Inc. It's that simple.
I don't see one as much better than the other, they're just two different phones for two different niche's.
The only issue I have with the X is the locked bootloader. I personally would never pick one up because of the size (don't want a phone that big), but I would also be hesitant to pick it up because you may not ever be able to customize it like you can the Inc.
I haven't rooted yet (waiting for a very solid sense-free 2.2 rom), but it's good to know that if I want to, it's an easy process and I will have a lot of choices to choose from when it comes to customizing my phone.
We may even get gingerbread well before the X in the form of a custom rom due to the locked bootloader that, from what I've read, may never be cracked.