I love my 90 gal tank. The big pluses are the 18 in front to back and the 4 foot front. It gives me the space to really do something. Don't get me wrong, many of the small tanks can be real gems, but my 90 can look like that across the room.
Is it worth it? Well, the comes down to how much do you want to spend and what do you want to get out of you system. For me, I'd do it again, for others the lower cost of the 55 might be a big factor. Personally, I think you get a much better effect using a 90 verses a 55. That larger volume of water doesn't hurt either, especially if you want big fish.
As for the aquascape, I don't consider a large tank to be much more difficult that a small one, Like anything else, you do need to select items so that they work in the size tank you are doing. For example, a piece of driftwood that looks great in a 10 gal tank is going to be lost in a 90. Also, when you stock a large tank you might use a lot more fish of the same species. 6 small tetras will make a nice school in a 10 gal tank, but you might want 30 of them in a large tank.
With a 90's front to back of 18 inches, verses a 55 gal tanks 12 inches, a 55 gal stand will not work. However many people build their own stands to save money.
