I need to decide between two windows for our house:
- Simonton 5300, double pane for $431 each, installed
- Pella 350, triple pane for $538 each, installed
Both have screens, low-E Argon, internal dividers, vinyl, etc.

From reading this discussion board, the Simonton's seem to be a better window and are cheaper in this situation.
Not sure if $100 more for triple pane is worth it. Thanks!

Thank you all for the advice! I LOVE this forum!

I think adding 100( better be krypton or its a bit high ) for triple is worth it depending on the base price of the 5500 ( which I like better than the pella). Have you looked at some of the higher end brands such as Okna , Himark , Soft Lite, Gorell, or Sunrise ? All of the aforementioned brands will have better performance numbers both structurally and from an energy efficiency perspective than either of the two brands you saw and probably with similar pricing.
Depending on where you are located, most of these brands should be available.

I agree with mstrext, your focal point should be on the performace of the window. These things should be compared with each window: U(the lower the better0, SHGC(this values best is selected by geography), AI ( air infiltration, the amount of breeze through a window, the lower the number the better), DP(design pressure= how well built the window is, the higher the better).
At minimum i would look at the 5500, then as previously mentioned HiMark, Soft-lite, Sunrise and others.

+1. The pella 350 is a major upgrade for them in terms of vinyl, but in the mid $5's, you could very well get into the top level of performance in the brands mentioned above.
In Simonton, I'd look at the 5500 minimum, but again, you may be able to get better performance in your price range.