I think that the 8000 series is their best product.
The Preservation is essentially a Ultramaxx/Sheffield with more bells and whistles. Pretty bulky (less glass) and typically fetches a "premium " price because it is a private label line. The thermal number of .17 (triple pane krypton) while being a great rating, is less impressive when compared to other products that achieve .15 or .16 with better air infiltration ratings to boot. Regarding the "bulky frame" adding strength, look at it like the bumper on your car. Back in the 70's when crash test standards changed, we had these giant ugly steel bumpers protruding from the front and rear of every car. Now, they are much smaller, integrated into the design, and actually provide more protection. Such is a bulky window design. Newer models have superior engineering that provide equal or better strength/longevity while gaining glass area looking nicer. A great thing to look at would be the structural ratings of the window. The design pressure and air infiltration ratings will be very telling as to the manufacturing tolerances and strength of a given assembly.
On the Excalibur/Revere Berkshire/Enviroview, it has a welded in sloped sill, however it still has open channels that water is directed through and out weep holes. Basically, it doesn't have the "bulk" and glass loss associated with most pocket sill designs (or snap in sloped sills), but it does still channel water through the frame which is undesirable, as along with that water goes dirt, debris, bugs, etc that can slow or stop the water flow and cause all kinds of issues from minor to severe.
The are certainly far worse products than those mentioned above, but when considering a product, I like to look at the thermal and structural ratings, potential design flaws, and overall reputation of the manufacturer to determine where it falls in the spectrum of quality and performance. I can't speak for others, but that is why I sell, install, and recommend the products that I do and shy away from other choices.