Betta Fish: do bettas prefer dimmer lightning over bright?

my new son (Lucifer) arrived yesterday. he's in my 5g (will probably get a bigger tank once he grows and will DEFINITELY get a bigger one if he shows signs of stress..)

I have read that bettas apparently prefer a dimmer lightning, is that true? i have two lights, 5w and 7w.

for now I'm using the weaker light, since he's still a bit stressed out.