I had infratint done on my car and its quite good. I can't
comment on the comparison with vkool because I've never used vkool
before. Infratint is OK lah....make the car dark enough so that
people can't see you at night in the backseat. The guy who did the
tinting was also quite friendly and explains to you everything
before proceeding.
Price is also quite reasonable. My station wagon has a lot of glass
and I paid $200 only, for tinting of all the glasses behind the
front seats only. Price depends on what type of tint you
choose.
On the front 3 pieces of glass, I have something else which is not
so dark...but forgot what liow. This was done years ago.