Choice of Games (there are lots of them on Steam, usually called "Choice of [random name]" lets you do things like set complex variables, and do complex things to them, makes it easier to have large/long/wordy projects, supports more complex flow stuff. The advantage is you can do all that stuff as easily as you do any other choicescript scripting. You can do those things in twine but they require javascript knowledge. Choicescript is easier to learn, Javascript is the language used to make almost all content rich websites now. I am not familiar enough with how to stick javascript into twine to speak on any details.

Annnd that was probably more detail than you needed. In short, I think twine is the best choice for a little jam project, but if for some reason you wanted to branch out into something more complex for a more game-like story, Choice of Games is worth looking into.

Twine is a good way to just jump in (and also prototype!)

Javascript is a pain in a lot of ways, but it's not too terrible when you get over the initial hump. Do you have any programming or scripting experience?

Javascript is how almost all content rich website are built these days. So it's linked very, very closely to HTML and CSS (among other things).

If you want a simple place to start learning JS (and this is way outside the scope of the jam), i suggest you check out http://www.w3schools.com/js/default.asp