First of all, I have no experience with these tanks so this is just my 2 cents on them. I can't even see the 2nd tank listed, but I'd go for a 2.5 gallon instead of a 2. Not much of a difference, but still a difference. I'll point out some pros and cons of both tanks that I see by looking at them for you, until someone that's had these can offer advice :)
Petco 2.5 Gal:
It's taller than it is long though, which isn't usually a good choice for a betta- they prefer swimming side to side, not up and down, and it'd take them more time to get to the surface for air. It has a lid, but I can't tell if there's any holes for air, I'm sure around the filter is some space though. The reviews say the filter is effective and silent, which is a good thing.
This tank is longer than tall, has a secure lid with vent holes. You'd have to remove the lid to clean the tank. The filter seems to take up a lot of the surface area of the aquarium, and the way the lid is you wouldn't be able to get one that hangs off the side if you chose to in the future. I know this aquarium is acrylic, you'd have to watch that because acrylic scratches really easily, the first tank probably is also acrylic though :p I recommend reading the petsmart reviews online, they are quite helpful and I always use them, since the petco site has no reviews for this product. One person said the light is too close to the filter and resulted in a harsh algae bloom, you'd probably want to watch use of the light in that case. Here's the product page: http://www.petsmart.com/product/inde...436&lmdn=Brand
Hope I was of some help :)