I saw this thread a little late and didn't bother to read everyone else's replies (sorry guys). So this may have been covered already by someone else.
My current layout is ho scale. The first layout I built in my house was n scale though. So here's my opinion. Ho scale is definitely going to require more room if you want have more stuff on the layout. You can't build an empire layout with ho scale on a 4x8 piece of plywood. Also, everything costs more; buildings, engines, rolling stock, etc. But the level of detail, if that's a concern, is really great. Don't get me wrong though, n scale can have the same amount of detail but it seems to have to be added by the modeler. Ho scale is easier to handle, my fingers had a hard time with n scale equipment and tiny objects. My dad has a little arthritis and couldn't rerail n scale cars when he came over. So that's something you want to consider as well. Can you deal with tiny objects. I really enjoyed my n scale layout but ho scale suits me better. And that's the bottom line, finding a scale that works for you. How much space do you have, how big is your budget, and what do you want out of the layout. Those are the questions I had asked myself when I made the jump back to ho scale. And everything I want of my layout I have accomplished with ho scale. Sure I could have done more with n scale but for me the big part of getting away from it was the size of the models.