I have used both the MaxProp and the Autostream. Each has its pros and cons:

Maxprop:

Pros- proven and reliable
Cons- see Autostream pros

Autostream:

Pros- Stainless construction which is generally more corrosion resistant
than MaxProp's bronze. It has independent pitch settings for forward and
reverse which will compensate for a transmission with a different gear ratio
in forward vs reverse

Cons- This is a big one. The blades have less surface area than the MaxProp
and therefore have to be set with more pitch to compensate. This causes
cavitation when powering into a headwind.

Overall I would go with the 3 bladed MaxProp. You can get the VP version for
a few hunderd $ more which lets you reset the pitch without dissasembling,
ie a diver can do it in the water. It will usually take at least one try and
error before you get the pitch right. MaxProp's recommendations don't always
work.

David