That's a huge window in a bathroom that close to a neighbor's house. I like live wire oak's suggestion, or maybe there's something else you could do, like windows in sort of a transom position, up towards the ceiling. I understand the desire for lots of light in a bathroom, but if I were that close to my neighbor's house, I wouldn't really feel "comfy" in the bathroom even with a frosted or obscure glass without a window covering down. And that's coming from a person who has hardly any window treatments because I don't really care who sees what. Except in the bathroom, that's where I draw the line.

+1 Nothing Horrible about the Simonton window at all. Once you get into the upper end lines it tends to run a bit bulky and you could argue that the fit and finish aren't as nice as some of the other windows out there but I would never use the adjective of horrible. Foam filling, and its impact, depends on the extrusion, design, and realized U-Factor improvement. Some windows it makes no difference, others and make a great difference. Just depends on the window. You budget is a bit light if you ask me. The question I always tell folks is would you rather spend a bit more now for a great window and not have to re-do this project of go cheap now and spend again? You are dealing with that very issue right now in your current windows. The Euphoria of a "great deal" has long since worn off when you are stuck re-doing the work.

I prefer the constant force. The potomac is 3/4 stainless steel and very strong. the other is ok as well but the 3/4 constant force would be my choice if i manufactured a window. I always disliked the chord system but the newer ones are a big improvement. Both will last. Some guys mistakingly confuse the old spiral balance systems which i hate, with the constant force. 2 totally different balance systems. Only the low end companies still use spiral balances. That may be what the other contractor is feeding you. Another great window and one of the better windows made is soft lite elements window and they also use constant force and although its a good window like the others you saw, its mucho expensive. The contractor claiming the chord is better is using a sleazy type sales tactic.

We had triple sliders put in our lake house to replace triple double hungs. It really added a lot of light compared to the old double hungs and opened up the view. I think we used Softlite (vinyl). The sliding sections on each end lift out for cleaning which was a plus since they are high off the ground. I'm sure many manufacturers can do these.