I'm in the same boat as Ry The Fly guy, need new waders and am between the G4/G4Z and Patagonia Gallegeos.
Was in my favorite shop the other day talking to the staff about each. Consensus seems to be that you can't go wrong with either. Staff member showed me the seam taping on the Simms vs Patagonia, around the booties, crotch and so on. He knows when I do buy I will buy from his shop, so he took a few more minutes with me than I was expecting. we looked at both waders from the outside and then turned them inside out and compared the fit and finish on the inside.
Definite edge to Simms here, they just appear to be put together a bit more carefully. Everything lines up perfect. You can tell great care went into the manufacturing process whereas with the Patagonia they looked more mass produced.
Also with Simms gortex if you think you have a pinhole leak(s) or just want to check, this can be done easily by spraying the waders inside out with alcohol. Leaks will turn dark and can easily be identified and fixed (aquaseal). Unfortunately with Patagonia the inner membrane will NOT react the same to isopropyl alcohol so finding pinhole leaks will have to be done by more labor intensive methods (filling with water, etc.).
So, IMO, quality and serviceability (finding and repairing leaks) the winner is Simms.
However, if you need to send your Simms waders away for warranty work it can be a real nightmare. I personally had a brutal experience with Simms warranty department when I sent my G3 jacket to them. Other users on this site have had similar experiences so it is fair to say it was not an isolated incident.
Patagonia on the other hand seems to have an amazing warranty policy with their waders. According to the staff member, if they leak within in a year of purchase, bring them into the store and we'll give you a new pair OVER THE COUNTER (!) Then they deal with Patagonia to get reimbursed. I was floored when I heard this.
If they leak after a year you will have to mail them to Patagonia, but they have an office in BC, in Vancouver! So shipping is way less than to mail to Simms USA, and you will get them back a lot faster. Also apparently unless it is obvious you have abused the waders you mail in, they will likely just give you a new pair.
Conclusion: Simms has the better product and Patagonia the better warranty. I am still undecided on which I'll buy. It'll probably come down to the best fit. Before steelhead season I'll devote a half day to trying on and pick the pair I like best.
Finally regarding the old G3s vs the new G3s. I'm not a fan at all of the new G3s. Yeah they are lighter and maybe more breathable than the old G3s (which I have now) but I do not think they'll hold up well to how I fish (bush wack, trip and fall, etc.). If I could find a pair of new "old G3s" I would consider them for the right price.
I have never had zippered waders but I think I'll go that route this time. Just plain sucks trying to dig out your cold flaccid appendage with cold hands on a cold day.