Take a look through this post over at 40kforums, it pretty much sums up everything:
Personally, I've got some hexpots (and slightly newer round pots) of Citadel range (NOT new range), a few Reaper droppers, a bunch of Badger, Badger Spectra-tex, and Badger-Wicked airbrush paints, some Winsor-Newton tubes (thinned and put into 2oz bottles), 1 small can of latex interior paint (basecoat SW army), and Delco "Americana" craft paints. As long as it's thinned properly, the only factor on my line-up is usually coverage.
The paints are all generally the same. Go for the Citadel/Vallejo ranges for metallics, as they seem the best for that. But for general colors they're all approximately the same. Then it comes to price comparisons, availability, the type of container, etc. Pick your preference, and go with it!
I regularly attack my local hobby lobby for whatever paints I want. If the model ranges don't have the colors I'm looking for, I look elsewhere (hence the Americana Craft Paint, which works fine just doesn't cover to save a damn). Also keep in mind mixing is an option as well. I've got just as many bottles of paints that are custom mixed as I do original colors. And they're all water based (acrylics), so mixing between ranges isn't an issue.
Hope my opinion helps, and I hope you find the link I posted useful. Good luck
"It is curious that physical courage should be so common in the world and moral courage so rare."