Q: contrast for contact lenses?

Hi:

I've been using Proclear Biocompatibles for a couple of years, -2.00/-2.00

recently, my prescription was bumped up to -2.25/-2.25 and I have been
trying out Coopervision Frequency 55s... they seem OK, and I have noticed a
significant increase in contrast with these

Q1: is the increased contrast because of the lens (F55), or, because of the
stronger prescription? (my feeling is that it's the lenses, because I seem
to see generally things differently)

if it's the lenses themselves, which lens give a truer representation?

Q2: is contrast something to consider when choosing lenses?

thx!

-- Paul