what to do?

I'm really conflicted right now because in terms of exercise during the school year, I don't know what to do. I'm currently taking a "pilates" class through the IMA--and I put it in quotes because my instructor, Erin, usually teaches yoga so her style of pilates is heavily influenced by that. I have to say, I absolutely love my instructor! I like how everything flows from one form to another, how she always asks what areas we would like to focus on and really caters to that, how she focuses on loosening and warming up the areas around our joints, and how she emphasizes understanding our bodies' limits while still maintaining proper form. Usually instructors first demonstrate the proper form and then sometimes show the modification. Erin takes the opposite approach where she slowly eases us in with a warm up, and then while focusing on the right area and right muscles, slowly puts us into position and gradually increases it from there

some issues I've always had with pilates and yoga are my weak lower back and tight hips, but Erin really helps strengthen and loosen those areas. She's the only instructor I've had (and I've had my fair share) where I never look at the clock and I look forward to going to class. Hell, the only drawback right now is that the class is only twice a week!

my conflict is that once summer quarter is over, Erin will go back to teaching at Yogalife and the usual teacher will come back to teach pilates during the entire school year. I really don't like this instructor! I feel that my muscles tense up with her because she focuses too much on form and flexibility without much consideration for those who may need some modifications. She obviously understands the body, but sometimes focuses on too many muscles and joints at once that I get over-stimulated, over think it, and end up tensing up. It takes me a lot of self-motivation (and I mean a lot) to get myself down to the IMA to attend one of her classes. In the end, I'm either prone to skipping her class or I don't feel neither relaxed nor worked out like I should

but, it'd only cost me about $15/mo for classes 2x/wk, whereas, Erin (and the other instructors at the studio) would be about $90/mo for unlimited classes... There are more pros & cons I could list, but then I would never shut up. I'm currently leaning toward the latter option, but fiscally, that difference is soo much that I really need to consider this