So should you upgrade and what should you use?
It depends.
Replacing windows right before selling may not net the cost of their installation. It is typically only profitable if the windows are in great disrepair. You may not get a 1 to 1 return if the current windows are old but still in decent shape. Many buyers don't pay enough extra for brand new high quality windows to make it worth it to change out decent windows that still have life.
If, when selling a home, I have one window that is completely fogged and the rest look great, I'll definitely fix that one. People often get fixated on the one imperfection. I refer to this as the broken tile syndrome where the entire mosaic is perfect but there is one chipped tile and that's all anyone can see. Note: it may be less expensive to replace than to repair a window.
However, if I'm going to own and/or live in the property for years, I do see the value in replacing old windows. I justify the expense based on the following:
1. Increased enjoyment of living at the property with nicer windows,
2. lower utility bills,
3. increasing rentability, and
4. increasing the overall value of the property.
There is a huge range of quality. It would not make sense to put low quality but new windows in a $2,500,000 home. Similarly the buyer of a $250,000 townhome won't pay 25k more for that property even if the most fancy windows, costing $25,000, are installed in it.
Check with a LuxManor Realtor if you're not sure of how to proceed. We can discuss if it makes sense and what level of quality matches the home.