It really all depends on the venue and who is catering - usually, despite what most people think, a sit down dinner is cheaper; but again it all depends on who your vendors are.
I personally like the sit down dinners - I think it gives it a more formal feel and you don't have everyone getting up and down out of their seats; you just get everything served to you at the table. I think if you are working with a smaller space a sit-down dinner is much nicer and makes things seem less crowded. As a woman I know that I prefer the formal dinners - it can be hard to be in a fancy dress, high heels, etc. and trying to carry around a plate of food.