Compared to Slinkies, Cobalts will be brighter sounding and rougher feeling. Kinda like Rotosound 66's.
For the same price as Cobalts I personally like DR Dragon Skins but of course strings are a personal preference.
Heck, just buy a bunch of different strings and see what you like best! Check out www.bassstringsonline.com
where you'll get the best price and selection, plus a TB user discount