THe APC props don't tend to flex as much, and are therefore a little more efficient. If you watch a MAS, especially something like a 14X8 on the end of a saito 100 (the MAS larger props have white tips), you can actually see the prop flex as throttle is applied.
Anyway, MAS also makes a scimitar blade that is shaped more like the apc props (sharp, not blunt on the end)which also makes them more efficient. If you really like the APC shape, but need to go with MAS, then go that route.
Again, I run MAS on all of my saitos with no problems. For that plane, I might suggest you go with a 15 X 6