watercolor takes a bit longer to soak in as well on bristol, the water usually dries up before the pigment has a chance to spread and mix evenly, gives it a muddy look sort of. If you dont have watercolor paper, you can also try a brand like aquabee 92 lbs that has a bit of a tooth so the pigments sit better. But for that, i'd not really go over 9x14 as it will warp and buckle.
the most fun to be had can be with just watercolor paper though, if you like the smoothness and slick of bristol, go for a hotpress paper rather than a coldpress which is more toothy and rough. fabriano artistico makes my favorite. Lanaquarel also makes a very smooth/slick paper at hotpress, but its super soft and absorbent, so you've less time to work on it unless its on colder days- but your colors will mix very lovely.
awesomeness!! thanks! i bought a big thing of the arches paper for a job that never fell through, the block thing, where the pages re all sealed together...can you just paint on the sheets as you go or is it best to tear the sheets out and then paint on them?? thanks o' watercolor master!!!