Well, as hulio mentioned, both sides are amazingly beautiful, but there's a great difference between the two.
The Brazilean side provides you of a panoramic view of the falls. You have about 2.5km of a promenade, all along the side of the river opposite to the falls. It's a great short walk, that ends in the Devils throat, where's the only part in which you can get really close to the falls, and feel the power of the water.
Right next to the exit there's a great Bird zoo you mustn't miss.
The Argentinean side takes you between the falls, and gets you as close as possible, so that you can't even breathe. There you can also take a zodiac boat trip to get really close to the falls from the water level.
you don't need more than a day and a half there (half a day for the Brazilean side, and another full day to experience the Argentinean side) to see the national parks on both sides. Apart of the falls, there's little to see on both sides - maybe the power plant near Foz, on the Brazilean side, and the 3 Border point just outside Puerto Iguazu on the Argentinean side. However, these visit don't require more than a couple of hours each.
Regarding the lodging aspect of your visit, you'll find 5 stars as some low bugdet places both sides of the border. you can also stay at the Sheraton Iguazu hotel inside the park, just 300m from the falls.
Some more info on lodging and travel from my experience, you can find here: http://gabykaminsky.blogspot.com/2005/09/hello-from-iguazu.html