Since the OP asked for "better/tougher", Vol 2 is definitely the answer as the VF consensus is clearly that it's much tougher. I'm going to throw in a good word for Vol 1, though, because hardly anyone ever does.
I bought the Vol 1 & 2 combo pack from Ingrid's site in her recent sale. I agree the list price for vol 1 is too high, but the way I bought it, the price didn't seem bad. I started a rotation just this week and am liking it a lot. There are just the 4 DVD workouts on one disk, and they're 11-20 minutes, but I think they're a nice intensity for that length. I feel worked out with such a short workout, but no dread factor. The rotation adds 15-20 minutes of cardio each day, either on your own or using a simple HIIT workout that's included in the PDF booklet). There are two upper body workouts in the booklet that are quite simple and effective.
I do think vol 1 is a good place to start if you want to work up to vol 2, or if you like Ingrid and this style of training but don't want the length or dread factor of vol 2 at present, and can get past the vol 1 price or get a deal on it.