Yep I think the idea that C++ is slower is not accurate these days, it's similar to the idea the C is slower than assembler (modern compilers produce very efficient assembler).
Anyway I've been using C++ on my 1200 for a port of
DOTT.
I use StormC V4 which uses the GCC compiler and features an IDE with built in debugger which makes everything a lot easier. You can still buy StromC V4 new for about $50.
It will take you longer to learn C++ of course, I spent a year learning straight C before I started looking at C++.