Nothing rude about it. Pretty much standard practice.

Hi, I got a couple quotes for some roof work. The two companies had different solutions for 2 of the issues.

I liked the first guy better, but I want to ask him about something the 2nd company said. (Basically, the 1st guy said that the white roof paint wasn't as good as the silver aluminum paint so that he would paint it over with that. The 2nd company said that once you go white, you can't go back to silver because it doesn't adhere as well.)

So long story short, is it rude to question the first guy based on the 2nd guy's analysis?

Or do I need to look for guy #3?