We're in Eastern PA, and will be replacing about half of the 50-ish year old windows in our house this year.
Our most likely choice is the True View 6300 Series by Interstate Windows. http://www.trueviewwindows.com/html/new_6300_line.html
These would be double paned all vinyl with Super Seal, Low-E, Argon/Krypton mix. According to the mfr, these have a 3.33 R-value
We also took estimates from a local vendor selling Vista windows. I don't recall all the exact specs because the options were mind boggling, but I recall that they also used the Super Seal, and the window we would have been getting had an R-value of 4. They were also $2500 more total.
We did take a look at Champion windows, though I've seen in the past that Champion seems not to be well regarded here. Champion was about $2000 more than the True View 6300's. I don't recall the R rating of the Champion windows, but based on what I've read here I'm not sure that they should really be in the running anyway.
We are on a tight budget, but could be persuaded to the higher priced windows if I could be convinced that the .7 R-value difference is worth killing our budget for. There were some differences regarding the frame construction, but those differences seemed only to be cosmetic in their significance.
Any thoughts, either on the windows themselves or on the specs of the 6300 Windows? (more complete specs are on the mfr website I linked above)