Assuming you have actually seen samples of both windows, the Simonton would be the better buy. The Ultramaxx is a window that hasn't been redesigned for many years and is lacking in many ways starting with it's overblown boxy look. If you have seen a sample you will realize it reduces the glass more than any other window on the market that I'm aware of. It also employs and 80's designed snap-in pocket sill. Pocket sills allow water to drain through the frame and with the water also comes pollen, atmospheric dirt and debris and even dead insects. Given enough time the weep system on the window can become clogged with debris allowing water to fill up inside the frame leading to eventual mold and mildew. Additionally Solar60 glass has either 1 or 2 layers of LoE. I would also add that Alside does not have a great reputation for consistent quality.

Simonton Reflections 5500 has a co-extruded sill that has 3 steps in it, a much more intelligent design that allows rain to drain without entering the inside of the frame. This design eliminates the possibility of gunk clogging inside the frame. The LoE 366 glass gives you 3 layers of LoE which reduces the Solar Heat Gain. This is important if you live in a warm part of the country. Since you didn't say what kind of spacer you were quoted, I will assume it was Super Spacer since that is what is offered by Simonton with the 366 glass. You also have a 1" IGU included. Super Spacer is a non-conductive Silicon foam Spacer which is specifically engineered to expand and contract with the glass, therefore reducing the possibility of a glass seal failure and minimizing the potential for argon gas leakage. Plus Simontons customer service is absolutely top notch. Alside can be very difficult to deal with if a warranty issue arises. Often taking a great deal of time and effort to get warranty issues resolved.

Agree, the Ultramaxx is poorly designed and very bulky as is the sheffield. This window is used by contractors looking to offer the cheapest window.
Same goes for MI Windows and Silverline, total junk. Simonton 5500 is average and better than alside.
High end/ highly efficient windows would be Sunrise( vanguard), Okna , Soft Lite( elements),
Quantum 2 by Kensington, and Starmark.

This post was edited by mmarse1 on Sat, Apr 5, 14 at 8:59