For the slight price difference (a couple of dollars) I'd go with a trusted filter like an AquaClear such as this one: Aquaclear 50 Power Filter at Big Al's Online
You would always get the 30 (if it's for your 29g) but it's better to be overfiltered than underfiltered. Personally I'd go with the AC
50 if I planned on upgrading or the AC
30 if I had a bunch of 29g tanks and wanted to save $5 per filter. I'd pay the extra $5 if you are only buying one though.