Do not do one leg on the leg press.
I practice medicine and spoke at great length with a past classmate of mine who went into sports medicine. We also sat down with another budy of ours who went into Kinesiology.
There are certain muscles that were not meant to be worked on an individual basis; what I mean is that weight was meant to be as evenly distributed amongst the symmetric groups as possible.
Some examples of muscle groups like this were Glutes and Pecs.
We talked at great length about this and I don't really want to go into the logistics of this; I'm sure the information as to why is clearly divulged somewhere out there on the interweb.