Irv said
@Fiddlerman and others.  Sorry if this thread is a repeat.  If so, I have not seen it.

I enjoy playing the violin with a flesch chin rest which places my nose pointed toward the violin scroll.  In watching various Fiddlerman videos, I notice that your nose is pointed toward the right hand upper bout.  

The only ergonomic disadvantage I can surmise from your position is it would lessen bow reach for people with short arms (certainly not a problem of mine).  It may add a degree of facility on playing first position on the fingerboard.  

Has one method proven superior over time or is it a matter of custom?  Would matters change between violin and viola?

  

It's a matter of personal preference and depends on arm length and chinrest. People with short arms and people who use centered chinrests tend to point their instruments more forward, people with long arms and people who use side-mounted chinrests tend to point their instruments more toward their shoulders. (These are tendencies, not rules.)

I wouldn't advocate pointing your nose directly at the scroll, though -- the scroll being directly in your line of sight would make it harder to read music.

I've known people to switch as adults after getting a new chinrest. It does take some time. I'm in the middle of changing my viola position now after changing my chinrest last summer. I'm not making as drastic a change because they're both side-mounted chinrests and the new one only has its cup centered about a centimeter closer to my viola's center line, but that's enough rotation to affect muscle memory in both hands (especially bowing planes) quite a bit.

I should add: YMMV on the time it takes to change. For me it may be taking an extra-long time because 1) I have almost no neck and find every chinrest on the market too tall, so had to get a custom-made one last summer just to be able to fit a viola between my jaw and collarbone at all (thus a good viola hold was literally impossible for me before last summer), and 2) I'm recovering from a serious chronic shoulder injury that has affected my playing for well over a year.