If you're used to tracking already, try Impulse tracker 2
- you don't need a mouse
- fast hotkeys, fast editor
- NNA's (compared to Moonblaster it means that samples continue on the same channel when playing another note, it takes another channel internally, you don't have to bother about that then)
You want to choose between tracker & synth . That comparison is a bit wrong imho. You're comparing a composition-method with a synth. Ofcourse you can buy a synth.. but how do you control it?
Tracker-users are like music-programmers (it's very close to classic notation) while Cubase/Logic/Cakewalk/Sonar etc. (to be called 'midi app') -users are more the players/performers.
The difference is that if I want a number of notes (and I already know which ones) then I simply put them in the right place using a tracker. A midi app means that you have to play the notes first, that't including all your play-errors/mistakes. You can go two ways then:
play it again (and I find all this a waste of time), or
edit. Once you start editing in a midi app you soon realise why trackers are way faster with editing.. hence editing in a midi-app is -to me- a waste of time as well.
What are the downsides of a tracker:
- classic trackers have a fixed grid
- the grid is ofcourse flawless in terms of human timing-errors
- you need to sample a lot of stuff in advance to have some decent soundpalette
- the soundcard might be a problem/downside in case of IT2 .. I can recommend a classic SB-live! (with genuine SB16 emulation on board, never got it to work right on my Audigy .. that's why the stinker is in my unused B-system for years already

)
The downsides of a midi-app:
- slower composing if you're a classic-oriented composer
- worse overview
- mouse-interface .. we'll speak again when you're suffering from serious RSI
The positive sides of a tracker:
- editing/composing/tweaking at lightningspeed (and not a nanosecond less!)
- a 16th grid is sufficient for 99.999% of all music.
- cheap! You don't need expensive synths that are outdated within a year.
- a tracker comes with it's own synthengine, in case of IT2 meaning a polyphony of 256, using 64 inputchannels, no multitimbrality limits
The positive sides of a midi app:
- if you're like a eral pianoplayer then you'll appreciate the 'livelyness' of working without a fixed grid
- they're more modern, more support for plugins etc.
- there's a lot of choice in midi apps .. and companies keep updating their stuff
I keep referring to IT2, but naturally there are more trackers. They're however ..'different' .. usually they are slower in terms of composition-speed, but offer more stuff like MIDI, plugins, DSP etc. For some reason the ppl who code those trackers really want to ignore everything that made IT2 great.
Finally, I'm functional designer of IT3 and IT4 .. (these are worktitles).. you can expect me to handle all the positive and negative points mentioning above

Don't ask me for releasedates tho..