I depends on you and how much you know these programming languages.
As far as I know Assembly,Basic and C are the programming languages[tools] to implement an idea in microcontroller.
If you want speed use Assembly.
If you don't ave time and you want to quickly get your project up then use C.
Else you can use Basic.
###PLEASE GIVE MORE INFO###
even on you microcontroller pat number and so.
OOPic has a compiler of its own and compiles Java, Basic and C like constructs to its own ASM code. If you didn't have bought an OOPic board and I would suggest PIC microcontroller ( www.microchip.com ) and C language. PIC is much more known and well referenced but is a little harder to code too.