Krylon Fusion is the easiest and thats what I did the first time. I just finished respraying all the parts I did in glossy black Fusion with some glossy black Lacquer. It looks way better. I found the Fusion gloss to be not as glossy as I'd hoped, but the thing that bugged me the most was in the sun it looks dark grey with no "depth." The Lacquer requires more work (i.e. sand, prime, sand, base coat, sand, clear coat, sand, buff, polish. Well worth it though.
In short if you're going flat black then go with the Fusion. If you're going glossy, go with the Lacquer.
Fusion I believe is an Enamel. They never come out as nice as lacquer.
If you go with the Fusion or other enamel and decide you dont like it, you can switch to a lacquer. Lacquer on top of enamel is OK.