You can get dressier tanks, in terms of finishes and that sort of thing, but in terms of quality, I've never had a problem with any of the mass-produced tanks. I'd spend more time shopping and thinking about filters, heaters and ultimately fish, than I would concern myself about the tank. I've even bought more tanks second hand than new and have never had a problem. One thing I would recommend, though, is take the tank and set in your basement, outside, wherever, and set it level, and fill it up with water. Let it stand for a day or two to see if it leaks. If it passes for a couple of days, you should be good to go...
The general rule for tanks, is bigger is better (or size DOES matter). All things equal, I'd do a 46g tank over a 30g tank. Generally, they look better the bigger they get. Bowfronts are nice and if I get another 75g tank, I'll probably go bowfront. But, if you are planning on putting your tank in a corner, then a square tank may be the best bet. So, the tank choice issue is the same you'll get for just about any question you pose, "It all depends".
So, what kind of fish do you want....
Val
Edit: Woo Hoo, my 300th post. A big deal only to me...