I've had both, and the stock motors really aren't that bad; they will last for awhile and are relatively cheap; a heatsink is a good thing for those. No problem at all, but I would definately vent the canopy as well, as they do get hot and hot is bad. Fly for a battery pack, cool for the same length of time, fly. . .

The XTREMES are the only other brand of motor I would go with; I have no experience with the Vortex ones, but been here long enough to hear people say they are cheaply made.

The XTREMES are open top ventilated, ball bearing, so if properly broken in MAY equate to longer flight times; are slightly quieter, slightly cooler running, argueably more powerful; noteably more so if You get the shorter lived, softer, but more powerful silver brush replacements. A heatsink is still good, but not required, IMO if weight is a concern. You do have to still watch the motor temps. One can't become overly confident because You can get them hot and shorten the life span of these too. The commutator is pretty thin, so I wouldn't think that You can just keep replacing brushes and never have to replace the motor; they will wear out, but I think You can get a longer life than You can with the stock.

Motors are easy to replace; so whatever You think.