To each their own. I prefer AVR because the compiler is free and there's a lot of open code out there for RTOS and Libraries. But if you are brand new to programing, that won't make much difference to you right away, but once you get going it will enable you to do lots more, and even learn more.
On the language department, I love C. If it can't be done in C, it can't be done at all. That and C will teach a lot of things that you might not learn using other languages. In the end though, if you want a language you can use anywhere, from your Robot Project to the Linux Kernel, to Tractor Software (trust me on all that) C is the way to go.
So in summary: If you want to learn how to program, use C. If you want to get stuff done and don't much care for the programing, try to find something simpler, but remember it will most likely have limitations.