It really depends on how you like to play and what's important to your game specifically. I like having both, but I wouldn't push that for everybody.
Get Together has a great world and pre-made characters, and clubs can be really nifty both for making goals easier to accomplish and for just filling out the world with sims doing various things and showing up places. I usually end up changing a lot about the pre-made clubs, but that's okay and actually part of the fun for me. Sometimes clubs can get annoying, in them automatically trying to do things when that's inconvenient, but that can be dealt with and tweaked as needed pretty easilly.
Get to Work is cool if you like spending all day with your sim, and like weaving a story around specific tasks. If you HAVE a story you want to tell where your sim is a doctor or a detective or a scientist, I'd say it's totally worth it and probably a must have. Early on shops were a big let down for me, but most recently I think they patched it a bit and I've had great fun and success with that. I had a sim with the collector aspiration for instance who ran a very successful knick-knack store, which was pretty cool. I also LOVE ALIENS, so that's a big draw for me lol.
So, yeah, as you can see, it kinda depends on what your style is. GT maybe has more general application? Whereas GTW is a little more specialized, and might only be a benefit for specific stories. But again, if those happen to be the kind of stories you like telling, that might be a bigger draw for you. Good luck!