Well, the 10xl will obviously be a little slower than the 9xl at the same voltage. If that's OK with you, or you can up the voltage a little to compensate, or don't mind gearing up a tad to compensate, then go with the 10xl.

How about the feigao 540 8xl is that getting too hot?

I assume you are going with 4s? The 8XL should be perfectly fine with that.

8xl should be fine. Have you contacted Mike to see if he may havea 9xl around maybe? But on 4s, an 8xl would be better anyway.