It's not the language that is important, it's the programming style(s) the language supports. With Scheme and Java, you get a functional language (and one in which other paradigms can easily be implemented) and an OO-ish language. Pedagogically, I think that's superior to a sorta-functional-and-sorta-OO language and a OO-ish language.
I had a different experience in 6.034 than you did, I suppose. I think Scheme suited the class well and offered a nice way to express searches, minimizations, and decision systems. I'm sure you can do everything you can do in Scheme in Python but you could also do it in Java. Functional languages are particularly well-suited to these tasks. I wouldn't necessarily pick Scheme, though. Why not use the most appropriate tool for the job? If students have to learn a new language, OK. If you really do think Python is the best tool, OK.