Crist,
It is a good question that I don't completely have an answer for. First the watt rating of a motor is sort of a "burn-up" quantity. It certainly isn't where that motor will run nice and efficiently.
When I was going for my Nobler (after the Super Clown), I had a rough idea about what I needed to make the Nobler fly (rpm and prop size). I knew that the AXI2826 seemed to be a defacto standard for CL stunt (based on what other guys were using), so I guessed that was nominally what I needed. I began to look at RCGroups Electric forums, and about that time Scorpion had just come out with their kit motors. Also they provided tables of the motors with props running statically with currents, watts, voltages and rpm. So I just crossed correlated that I needed about 10krpm on a 10-6 prop to fly the Nobler, and that the total power package weight shouldn't be a lot more than my Brodak 40 with a tongue muffler and a 4oz (filled) fuel tank.
So I looked at the Scorpion 3014, 3020, and 3026 motors (sort of equivalent to AXI 2814, 2820, 2826). When I looked at the weight difference between the 3020 and 3026, and how they handled power, I decided that the 3020 made sense. It turned an 11-5.5 prop just great (what my mind had gravitated to after flying the Super Clown with a 10-6) .I also bought a 3014 kit at the same time. One thing to remember, it is easier to get a low kV with the bigger motor (fewer turns). In the Scorpion line, the 3014, 3020, 3026 weights are 4.3, 5.5, and 6.7oz respectively. The Max wattage ratings are 600, 800, 1000 respectively.
I have also flown the Nobler with the 3014 and it flies just fine with that too. If I was going to buy a new motor for the Nobler, I am thinking I might just go with the 3014. Recall that my level flying wattages (input) are in the 250-275 watt range, and only briefly peak into the 450 watt range. Since the wattage rating as I mentioned are continuous burn-up type ratings, I don't think I am stressing the 3014 at all. Now whether the 3008 would work well or not I am not sure. At some point you do need to balance the plane! (also the 3008 is still less efficient than the 3014, and at some other point, you need to make up for inefficiency with bigger (=more weight) batteries. So for me, and my choice of 18C 2100 cells, the 3014 and 3020 will certainly keep me happy for planes in the glow 25-40 range.