I have looked at the Imperial LS, and am wondering what are the REAL differences are between this window and the mid line vinyl Serious Window or the Simonton 5500 with superspacer and argon gas.
Don't know the mid line Serious very well but the Soft-Lite Imperial is a very well regarded window in the vinyl replacement market.
Very airtight and well built.
The 5500 is a solid performer as well, but does not have the stellar air and thermal data that the LS does. Not a fair comparison for the 5500.