Larry,
Although price is a "feature" to be sure, for 35 size planes, I think motors in the "28" or "30" mm diameter (armature) and magnets in the 14-20 mm length have plenty of moxie for our applications (e.g. AXI 2814 or 2829, or Scorpion 3014 or 3020). As the plane moves up in size to the 40 to 46 glow equivalent, you may think about the 26mm length magnet size (AXI 2826 or Scorpion 3026).

The ability of a motor to shed heat (at the upper levels of their application range) is determined by their surface area, which is why you see the longer (and wider) motors rated for higher power than the shorter (and narrower) ones. For example, the AXI 2820 and Scorpion 3020 are rated for max powers in the 800 watt range. My max power that I have seen on my ENobler is ~474Watts for a very brief period, so I believe we are really NOT stressing these motors. One reason I chose the 3020 over the longer 3026 was that I saved 1.3 oz in motor weight. I am guessing the 3014 would work fine too (and would save me another 1.1 oz). There is about an oz. difference between the AXI 2826 and 2820. One other detail is that there is a little less flexing along the motor shaft with the shorter length motors, but I don't think anyone is having an issue up to the "26" length sizes.

What depends on brand is bearing quality, permanent magnet strength (and temperature rating), lamination thickness (thinner the better). I don't think you can beat the AXI in terms of its quality (speaking about outrunners so as not to start an in-runner vs out-runner war!!). However if you want to get started in electric without completely blowing the bank account, there are much less expensive "good" quality motors which are just as powerful and efficient as the AXI. My guess is that they won't last as long as an AXI (or the equivalent--there are other excellent quality motors)---bearings may wear out, things like that. Anyway that's why I chose to play with Scorpion motors, they are pretty good quality, and are about 1/2 the cost (I think) than the AXI---especially if you consider you get everything including motor mount, prop shaft adapter, bullet connectors in the basic price. That lets me play with the 3 motors I have (3014, and two 3020's).

Now there are "Uber" cheap motors, and I haven't gone for those. There you might be worried about QC and construction quality on the very short time scale (like first flight). I have shied away from this end of the spectrum mainly because I do want something that works---at some point you are risking a reasonable investment, and there is no reason, I think, to go overboard---at least more than I already have

Larry,
I think "better" is a difficult thing to qualify. It (2820 vs 2826) would be a little lighter but a little less efficient (converting battery power into prop thrust), so it isn't clear to me that you would notice much if any difference. However in the future (on an new setup) you could save a little money on the smaller motor, but for something you already have, I'd say to stay with it.