Replacement vs. New Construction

[kona]

I am considering both vinyl replacemnt windows and new construction style windows and have recieved a bid for each. I live in Connecticut.
The replacemnt style vendor has been in business for 2 years, and the new construction for just under 50 years...a profound difference, I know, and a red falg to me right from the start.
The replcement wrapping he is proposing is (due to trim style in place) being altered; indeed, he is suggesting not wrapping at all but using a thin piece of vonyl trim that snaps onto the frame and is caulked into place.
another concern is a metal rail that the sliding window tracks on (swing and clean, the manufacturers term... Alside Windows)

thye replacemnt style is by Highland Window Co. (www.highlandwindow.com)
and the new construction is Mercury Excelum installed by SWI Glass and Metal (SWIGLASS.COM)

Any opinions on the which is the best for this climate zone and opinions about the two contarctors and/or their windows?

Many thanks!