Pure Barre and OT are two completely different workouts, different atmosphere, different energy levels...different everything.
OT is high energy, focused, fast, and competitive. You'll see results pretty quickly, but it takes a lot out of you. When I was an OT member I did it 2-3x's per week, and also did barre (Bar Method) as a complementary workout. Sort of Yin and Yang really. By the end of the week I was burnt out.
I have since stopped doing OT and BM, and discovered Barre3 which is a great combo workout. Cardio+Strength+Flex+Core.