I'm a huge fan of PTI's white. I prefer to shop elsewhere when I can, so I finally found Neenah 110 at a decent price and I actually prefer it.
Gina K's white is probably my favorite of all, but I just can't use it. It is so dry where we live (humidity hovers between 4-7% most of the year) that no matter how carefully and how much I score it, it almost always cracks. I don't think that is true of her colored paper. I think I used it the other day without a problem.
So, my vote is that if you can find Neenah at an affordable price, go for it.
Otherwise, use what you can and no worries. Truly. If someone is complaining about the quality of the GIFT you're giving them in the cards you make, I'd reconsider if I wanted to give that person cards.