I do not think Crestline should even be mentioned in the same sentence as Pella, Marvin, Anderson , or the other premium products. They are an ordinary contractor grade product in my opinion, having replaced many of their rotted double hung windows that were in houses only a few years old.
Absolute crap go with a marvin. Finally fiberglass patio doors are the hot current trend. I'm not sure if fiberglass come sliding but definately french opening. Go to a company that specializes in windows and doors. LIke a glass company in yellow pages. They are usually very reasonable with installation prices.