Looking at the vytex website it does appear to be a solid offering .

I don't have experience with the product, but those are good numbers. If I'm not mistaken, the Vytex Fortis is a notch better, but again, those are very solid ratings assuming that u-factor is for double pane glass, and is obtained without a very aggressive low-e that would lower the shgc too much. An SHGC of .25 or higher would go well with that u-factor in most heating dominated (cooler climate) applications.

After looking at the site it seems the Potomic is their best but the fortis is right up there as well. Both have mortised sill walls and I am pretty certain the Potomic is a Deceunic extrusion. Their patio door looks solid as well.