They are all three excellent windows..........I think it boils down to which one offers you the best deal on a big purchase and offers the style (interior and exterior ) that you want. I've used all three and had nothing but good results both in product and service.. Both Pella and Marvin have an excellent field consultant if needed and yes I've had to have their rep in the field......not because of a defective product, but because the framers did something hinky and I wanted a rep from the window manufacture to see the condition in the field before we installed the windows. Both had a rep on site within 48 hours.

None of the three are cheap though........be prepared to pay some big bucks. That's why I mentioned which one would give you the best deal on the large order.

Marvin is best of the three at custom fits...Pella only builds to the 1/4". No help with Kolbe...

Not a professional, but I'll weigh in that we LOVE our Marvin windows (seven floor to ceiling ones custom sized for a sunroom/great room addition).

We use Pella frequently and have been very happy with them. We are in process of converting a screened porch to a sunroom and the windows were custom made by Pella to get sizing. Did a wonderful job and each one fit like a glove. Marvin is a very good window also. Not familar with Kolbe either.

All 3 are excellent have all 3 bid and choose the best deal