As was alluded to above it depends of the flight regime you are interested in. If you are going for speed or endurance it is well worth it especially if you have fat tires. Lower drag means going faster. There has been a lot of work documenting the results, notablely the in Horner drag and performance book. Look at the full scale designs that have them, they have usually been thought out by careful designers and work as desired.

Usually in RC work the pilot makes enough mistakes that cause drag that the pants don't matter, but, if both pilots and airframes are equal then the difference pants bring might help. Do note as they also said that a knife edge wheel (which is mostly impractical on full scale) whe used on a model is a very low drag affair.

In a competition aerobatic machine it becomes difficult to make a case to add wheelpants. Great static thrust and light weight are needed. Lowest drag isn't necessarily a good thing when designing a constant velocity airplane.

Properly done they do look good though on anything.