There are certainly many anomalies and installation specific issues but I think its been pretty well demonstrated by many people that Gen II will perform better in noisy environment. BUT, to get that performance, you need Gen II all the way through, especially on the PIM. You can not just insert a Gen II device and expect the network to be better (not saying this is what you have, just saying in general). Gen I and Gen II should interoperate fine, but if starting from scratch just make sure all the stuff is Gen II.I've been told that the rectification of the issue is most likely not a GenI/GenII thing, but more likely due to manufacturing and programming differences between the brands.
I also just wanted to point out for the OP that if you do go wireless, there are also design considerations. To have a reliable mesh network, you need a good mesh. That means several switches need to see each other to build multiple paths. In a very large house such as your this can be problematic with just a handful of switches. Figure 30, maybe 40 feet as a max distance between switches. The point is, don't expect to have a handful of switches scattered around 8000 feet and have it work, and if it does, be super reliable. You need a good concentration of devices in that size to have great reliability.