Forum/internet connection/NSA ate my reply. So in short:

Never worked a call center, have worked 1st level support for a software firm. Ostensibly same thing, I had a phone, made/received calls regarding customer issues. As @Papewaio says it's all rinse and repeat. Most of your issues and calls should be straight forward, and the more straight forward the better, makes your job easier and your hours less stressful. Problems start when you add in the assorted arseholes/cretins who call or you have to call into the mix. Additionally if your workload spikes exponentially expect stress; having more tickets than you can be reasonably expected to handle is draining (same in all jobs I suppose though.)

And for me personally, I found dealing with other people's (usually petty and self-inflicted) issues vastly unrewarding. I'd much rather be actively involved in my own or my team's project and issues that directly relate to me and my work. But, this may not be the case for you

Anecdotally, outbound is harder. Several friends have worked them and their experiences do not sound fun. You have to be quick on your feet to diffuse the abusive and aggressive customers you will deal with. They love to take their stress out on the invisible man on the other end of the line. Lines like, "your number was randomly generated by a computer, I'm sorry we disturbed you", will be your saving grace.

Good luck, and may it lead to better and greater things.