This is the new 3.5 gallon (approx) home of my first ever betta, a recently acquired VT named Sid Fishus:
The ornament looks huge - and it is! But it's a cave underneath, and Sid just loves lurking in there/ swimming in and out of all the gaps. I'll have to move it to vac the gravel, but that's okay.
I like the Dymax IQ5 for my beginner fishkeeper's tank because it has adjustable heating/lighting and is acrylic, so it's very light. I bought Sid a stick-on leaf hammock so he can rest close to the surface to make up for how vertical it is, and he really likes that. The rest of my household is highly amused at the idea of my fish having a hammock, as well as the way Sid loafs around on it.
I also have the IQ3, but I do think it's too small - just over 2g and taller than it is wide. He seems much happier in this tank. The IQ3 might be fine for a medication tank when I get its heater replaced, though.
Sorry for the crap quality picture - taken on the iPod..