Ultimate clad's are a full frame window generally new construction or full ripout of existing window and the Infinity is a replacement type or insert windows.

Very different windows. Ultimate Clad is a aluminum clad wood and Infinity is a fiberglass product. Both are very good products.
Did you get the replacement casement quoted in the Ultimate line? Which one do you like better? If it is the Infinity, is it is worth the difference? I think only you can answer that.

The quotes are for a full replacement on my windows. I guess what sticks in my mind is the clad still has wood and has the potential for rot down the road. As for the Infinity it does not seem there is anything to rot on these windows although I am not sure which finish will holdup better in the long run. Another positive for the Infinity is the outside can be painted if necessary down the road not sure that is true the clad. So not sure what is best longevity. Both appear to be solid windows. I am more impressed with the clad dealer who has communicated installation procedures and what happens to minimize damage to the area surrounding the windows on the interior which will leave paint and wallpaper in tact when the job is done.

The clad window can be painted as well.

Typically the Ultimate is more expensive by comparison but they are both great windows. You can't go wrong with either.

Just get the right product for your application now and make sure that your installer knows his craft.