Everyone is different and so many factors dictate the best split/frequency/volume for bodybuilders. Me personally I think the more you can train a body part and recover effectively the more potential for growth (common sense). Obviously if you can train 104 times per year and recover each time it's much better than 52 times. However many of the best legs of all time were built with once weekly training. Most of the guys I know with the biggest legs usually train once weekly and it's one huge session. However there are many exceptions and no right answer and I would recommend more volume/frequency for the majority of people.
It will all come down to your volume, intensity and recovery abilities. Many need more recovery days than others. Everything from nutrition to rest/sleep come into play as well. It makes sense if a guy is eating 100% consistent nutrient dense foods, using effective intra nutrition, taking lot's of aas, hgh, inflammation aids, sleeping lot's and getting frequent tissue (massage) work done he can optimally recover and push the frequency more than someone who isn't doing those things.
Again everyone is different and sometimes plans can be tailored for your exact needs. 2 full workouts may be good for many but others may be better with 1. Some may do quads twice and hams once as another example. Me personally when everything is in place I prefer to train legs twice per week (well every 4 days or so). That could be hitting everything hard each session or perhaps one session is more quad focused (lighter hams) and the next more ham focused (lighter quads).
There is no right answer and it will all come down to all the variables I mentioned above. I should add you can also rotate volume/frequency and also train/improve your recovery abilities over time. Some "overtraining" isn't always a bad thing and the body is capable of a lot as long as you have everything in place. If you aren't resting or eating optimally I wouldn't bother though.
I will state generally speaking I have found most respond optimally to brutally hard training when it comes to legs. Higher reps but heavy weight and lot's of intensity and a fair amount of volume as well. Volume can vary depending upon frequency but through the week quite a lot of hard sets if you want them to really respond.