There's tons of choices out there, so it's hard to say. I use Dynagro Grow, and Dynagro Bloom, which are chemical ferts. I chose them because they contain all the essential micro-nutrients, in addition to the 'big 3' (N-P-K). I also had to watch what I spent, and these ferts have good 'bang for the buck'. Alot of people choose organic ferts, and swear by them. I've never had the chance to use them yet, but will when I need to buy some more. They say that organic ferts leave your bud tasting a little 'cleaner' which makes sense, so that's the main reason I want to try them.
That's just what I use. I'd say to wait and see what types other growers are using, then decide for yourself.