Your first link didn't work for me but here are my thoughts on the others:
* Aqueon mini-bow 2.5g - comes with an incandescent bulb - incandescent runs hot and usually it's better to get fluorescent
* Marineland mini-bow 3g - looks pretty nice, comes with LED bulbs, which are supposed to be expensive, not too bright, but nice
Both are acrylics - supposed to be clearer than glass and less distortion, slightly better insulator. However, apparently it's easily scratched. Both are curved on front, it looks like? That might make the fish look slightly bigger.
* Marina Mermaid 2.65g - plastic, and I am personally not a fan of brightly colored girly decor =)