To be honest, I don't really know that much about different types of yoga. I only know the term Ishta because it's the type of yoga that the people who produced the DVD I use practice (Yoga Zone). It's basically holding poses and tying movement to breathing and getting you to focus on your form. I don't really get too much into the mental aspect because the one guy really annoys me, but I like the routine. I have some other DVDs from the same group focusing on various aspects (abs, power yoga, etc.) but I don't use those nearly as often. The flow vinyasa DVD workout is intended to burn calories, and takes you through groupings of poses like an aerobic workout. I used to find it quite challenging before I started running, but not so much anymore. I use the first DVD the most because it resembles body weight exercises the most due to holding the poses.
There are a few people here (Ravi and nicole spring to mind) who know a lot more about yoga than I do, and I bet they'd be happy to help you figure it all out.