healthy-wise: which keyboard is better? there is a apple wireless keyboard and the apple keyboard with numeric keypad.

Which one is better for the overall healthy of my wrists and arms? I suffer from RSI and I want to buy a wireless keyboard but I'm afraid it will injure me.
I would highly recommend getting a natural ergonomic keyboard. Here is a link that Microsoft has explaining the difference. 
Ergonomic Keyboards

There are numerous keyboards that are ergonomic. Microsoft and Logitech have a few that work with Mac's.