I'd think the tank kits, like the 2.5 Minibow, would be best as the cats couldn't get into them with the hoods on and they'd be too heavy to knock off easily. The only thing to worry about in that case might be the cords. I have two 3-gallon Eclipse tanks that I personally really love.

Any betta container really should be lidded (with air holes of course) however, as betta fish can jump quite well. There have been a few sad stories on fishforums.net of people finding a dried up betta laying outside their bowl/tank.