I've always done my one-legged pedaling with the purpose of 'smoothing' out the pedal stroke for each leg. Using one leg really 'amplifies' inefficiences. I try to use a gear - usually low 70s - that allows me to start singlelegging at, and keep a cadence of, the mid-80s rpm. Once I start getting choppy and the stroke starts breakin down, I take a break, go 2-legged and then switch over to the other leg. Continue til the start of each rep is already choppy. No sense ingraining more bad muscle behaviour...
My left leg is a bit choppier than my right, but not enough for me to warrent more/'special' effort on that side. Having a dominant, more efficient side seems 'natural'; but this is a totally subjective, unsupported belief. I've not ever found any real research covering differences in legs. They may exist, I just haven't read any.
If I had a big difference (to my mind), I'd prolly consider using a different gear for the less trained leg, start and end the 'session' on that leg. That would give me one additional 'rep' with that leg.
Now that you bring it up, I'm gonna 'measure/time' how long it takes for each leg to get choppy - I might end up with a surprise.
I've never tried to use this as 'strength building'; but I guess there's nothing that should say pushing a big gear, one-legged, is any worse than pushing weights in the gym.
I still think the big bene is efficiency training for each leg...