Anyhoo... regarding 6x a week versus 3x a week...
My two cents on this matter would depend heavily on 2 things:
1.) The number of sets/reps
2.) The general environment of daily "stress" you deal with
(Of course, I am referring to 6x a week full body, not 6x training a week but splitting it into half-body exercises, making it just a split 3x a week routine)
First, #1: the number of sets and reps. All other things being equal (like diet, rest, etc.), whether you do 6x a week or 3x a week wouldn't matter much if the number of sets/reps are the same. So if you do 3x a week 2 sets each, that's just the same as 6x a week of only 1 set each. At the end of the week, the muscles get trained the same number of sets/reps. No big deal. Unless of course you can't manage 2 sets at 3x a week due to some other factors: eaily fatigued or heavier weights.
But the point here is, if the number of sets/reps remain pretty much the same, then virtually no difference.
But performing 6x a week with the same number of sets
per workout as 3x a week would mean the muscles are getting more work (6x a week 2 sets each versus 3x a week 2 sets each). Generally, if your diet can accomodate the stark increase in exercise, then more volume still spread out evenly would mean more growth. But this doesn't always mean
noticeable hypertrophy. Also, due to more frequent loading, your increments might have to be a little higher than regular in order to stay ahead of RBE. But on the other hand, given that muscle adaptation isn't instant and it generally takes around 7-14 days, that wouldn't be a problem unless perhaps if you repeat a weight often, zigzag a lot, or your increments are low.
In the short run, it may not matter so much since noticeable hypertrophy may not differ so much after a cycle or two, but in the long run, the rule is, all other things being equal (diet is still ok, fatigue especially CNS fatigue is managed well, etc) more volume would be better, unless the difference in volume is pretty small. We don't say less is better because muscles like less stimulation, but because it helps us manage everything better, makes us better able to keep things (that is, bodybuilding elements) from falling apart. So if you've been training for 6x a week with significantly higher volume than the standard 3x a week, and you are still able to maintain a diet proper for this and also manage your fatigue pretty well, go ahead. May not produce noticeable hypertrophy immediately, but if you keep it up well, in the long run it most probably would.
Now, #2, the general environment of daily "stress". Not just bodybuilding stress/fatigue is important. If you live a hectic daily life because of a super busy and stressful career where you are on-call 24/7 (like me), that is a whole different story. Chronic fatigue syndrome can be caused by non-physical causes, and adding frequent bodybuilding to the mix makes your chances of escaping it far lower.
My point there is simple: sure, you may have a great diet, and are controlling the volume for 6x a week training excellently, but if your life outside bodybuilding is toxic, then your body deserves more rest. This is not for the muscles. The muscles don't care how much crap you get in the office, they're good to go after (or at the peak of) protein synthesis no matter if the boss kicked your butt at the office and the wife don't want to
get it on at night. But on the opposite side, the rest of your nervous system needs a rest. They don't care about protein synthesis, they care about you getting over the stress produced at work, at home, and everywhere else.
Hope that helps. Just my two cents
-JV