Just speed of cut.

I just ran through some figures, and for a standard polished HSS drill suitable for soft alu, gives aprox. 2500-3100rpm.
The recommended feed rate is 0.19mm per rev, which equates to 475 to 590mm/min feed rate.

To acheive those feed rates, requires 450N of thrust and a 0.25kw spindle, and that's with a sharp split point drill. With a dull standard point drill, those figures rise to nearly 700N and 0.33kw.

However all those are theoretical, and just provide a best case to start from. Experience and experimentation on your particular machine will find the best for you.