If by 'good location' you mean center strip, then no Wynn/Enore. After that it's up to personal taste & budget. I would select Cosmopolitan because of the great rooms, balcony, and fountain view. (but I am biased becaused I just stayed there for 5 nights and had a great experience.)
City Center hotels will be more expensive than their counterparts like Planet Hollywood & Paris.
Again, it's up to personnal style & budget. To me the wynn/encore, bellagio & mandalay Bay did have a similar style, like luxury european interiors. The city center hotels seem to have a more modern style, with a mixture of dark and flashy colors. The rooms are also full of technology if you like that.
Will you be using a car? If yes then Cosmo has a big plus, if you don't like to walk far ;-) (see my review in the cosmo thread)