Both TTS and SI are basic drum synths to get you started.
Most folks have bought one or more of the more advanced, and better sounding synths available. These VSTi's have larger kits, a greater number of kits available and give you tons of options such as being able to build your own kits and tune the drums in those kits.
I picked up Jamstix years ago.... I fell in love. JS also has a list of drummers, each playing in the basic manner of a certain live drummer, and you can also select a playing style on top of that. The best thing to me about JS is that it can easily create the drum track for you. Select the drummer, kit, and style, and JS will do all the heavy lifting for you.
Since I started using it, I have not written ...or attempted to write, a drum track since. Oh yeah, if you don't like what it plays, you can have it play the measure or two again doing something different....and you are always free to edit manually in any measure in the song.
I don't always use JS these days, having found some other ways to create drum tracks.... but from time to time I go back to it because it plays well, and in a loose indy style when my others won't. This is one of the songs that I used JS on the drums:
http://soundclick.com/share.cfm?id=11198785I think it's a small dry wooden kit. Samples in JS are very well done.
hope this gives you some ideas.