Does brand of paint matter?

[Mary Sparrow]

I'm a self taught artist and would really like opinions on paint..does it really matter what paint you use (brand wise)..is the more expensive always better? What about the new water soluble paints? I have always just used the basic Winsor Newton or Grumbacher oils because that is what is available to me in this small town..but no matter how I try, my portraits just don't seem as vibrant as I would like for them to be. I am wondering if I need to spring for the high dollar paints, or if the real problem is with me and I need to learn to manipulate the paint better?

What are your thoughts and what do you get the best results with?
Thanks.

Mary