The Robert and Jean Hollander translation is better, in my opinion: better verse (James is a bit free, which is lovely, but ignores the terza rima, whereas the Hollanders do not) and way better notes, really, an astounding plethora of notes, valuable to both the general reader and more specialized folks. The notes and other apparatuses get you quite close to Dante's medieval theology and outlook, all without pearl-clutching over its Catholicism and antiquity and distance from our worldviews.
The Hollanders also include the Italian text, which is nice to have for comparison even if your Romance languages or Italian aren't great. I've taught them to both undergrads and a Catholic nun, and they worked wonderfully.
The Ciardi translation is a bit dated, but quite serviceable: WW Norton used to publish it in a lovely little hardcover, which is how I first read Dante.