Hi there, I was a post bac student and actually had both professors last summer. It's a tough call in who to take, they both have pro's and cons.
Peeran is by far the better professor. I learned a lot from him, and you will (strangely enough) thoroughly enjoy class. Everyone I know that had him liked him as a person and professor.
The only problem is that his class is hard. The tests are really hard, and even though I did well, I sweated over them.
Thomas on the other hand, isn't a strong a professor. He's a nice guy, but young and can rub some people the wrong way. His lectures are boring. He has slides and it's dark and you can't help but fall asleep. Peeran, on the other hand, is all lecture and is great with questions and examples.
But, Thomas's class was much easier. There are many grade boosters, like homework and quizzes, which are basically attendance quizzes. So it's hard not to get an A if you don't put in the work.
I ended up choosing thomas for my 2nd semester. It was a touch choice, but my main goal was to get to med school, and getting an A helped me more than learning orgo better. Either way, if you work hard enough, you'll be fine with orgo for the MCAT.
If you've got any other questions, please ask.
PS. Take Thomas for lab too, it's a little more regimented, but easier too.
