It is super legible , but a IF 
You need the light to be in an incident angle and create a highlight to the silver hour and minute hands to be able to see it clearly.
I have no problem with that but to some it can be annoying.
Would you expect to see a 5970P photo where the light didn't hit the right spot ;-)
Best thing is to check out the watch in metal or see if you can find someone who owns a 3970 Black Dial version to try.
Cheers,
CL