Intergity to Infinity is mostly aesthetics and options. It is a fiberglass window that can be had in all fg (both) fg with a fake laminate interior (Infinity), or fg with a real wood veneer interior (Integrity). My personal fav of the 3 is the Integrity with wood interior.
The Ultimate is the flagship Marvin product. Wood construction (multiple species available) with extruded aluminum exterior. Lots of options and customization possible. One of the most beautiful and well constructed wood products on the market IMO.

Homesealed covered it pretty well.
Integrity is a great product especially the wood ultrex. All fiberglass or wood/fiberglass. It's more suited for the new construction market but is still used for remodel work. They have many dealers, usually those who sell Marvin also sell Integrity.

Infinity is similar to Integrity more aimed at the remodel market and has a fiberglass exterior wood/composite type interior, or all fiberglass. they usually have dealers who only sell Infinity (but not always the case).

Marvin like mentioned above is the flag ship, more custom options, more high end. Extruded aluminum exterior with wood interior.

All around quality products. Just depends on your price point and options.