TTL or manual flash is really simply a personal choice, however you want to work.
TTL is more point&shoot. Sure, we can adjust it a little with flash compensation, but most newbies have not realized that yet... they feel like they have to take whatever they get. The Commander can even let us adjust a couple of TTL lights individually. But... it is often limited to only a couple of lights.
Manual flash, esp in the studio, typically means we meter each light carefully, to set its light level exactly how we want it to be, in relation to the others (lighting ratio, etc). We setup the lighting like we want it, any number of lights, and then we don't want no stinkin' computer messing with it.
Now yes, we can do some degree of that adjustment with TTL, certainly we can be more critical than point&shoot. But then when the subject turns their head, and TTL meters that differently, and we get unwanted variations, then we tend to consider manual lights.
Manual lights are much more tedious work, but nothing else can be controlled as well. A handheld light meter would be necessary. And Manual is nothing like point&shoot.