Fruity Loops is really easy to program, as long as your not doing any odd ball time signatures, then it can get kinda tricky, layering the patterns to play end to end properly(unless there's something I'm missing) Ez-Drummer Sounds awesome, but you have to program it in a MIDI piano roll, which can be very very tedious. But then you can tempo/time signature map your song in your DAW, and have a very continuous work flow. I think Plague Bringer Uses fruity loops, Or at least used to. The New Ghengis Tron album has Drumkit From Hell/EZ-Drummer on it. Another option if you're just doing drums and have no need for the synths/effects, is a program called Rhythm Rascal. It's a independently developed drum program that gives you total control over tempo, beat count, beat division, etc. for each pattern in a song. It makes it interesting cause you can go from a measure with steady 32nd notes on the kick, and then have a pattern where the hats/snare are occuring in the same time, but the kick is now playing 3 notes where it was playing four. And that one only costs about $30.
Edit: Just read your previous post again....I think Rhythm Rascal would be the way to go, ease of use and the sounds that it comes with would work pretty well for the type of stuff you're doing.
www.rhythmrascal.com