beauty is in the eyes of the beholder. The absolute best are probably Oxycheq and Halcyon but you're going to pay for them. $800 minimum for the Halcyon system. They're made in Florida and are top quality. I don't think they're worth the price, but many do. If you buy, I would buy from Extreme Exposure up in High Springs. Think Range Rover
Oxycheq systems run about $650 new from Cave Adventurers, they are again made in Florida and are of top quality, but not cheap. Edd sells them but any of the dealers should be around there. Think Land Rover
Deep Sea Supply is another top quality brand with everything made in California, just under $500 for those. As far as best bang/buck for a high end system DSS is the way to go. I like Oxycheqs stuff a little more, but to each his own. Think Jaguar
Dive Rite makes high quality rigs as well and is another Fl based company if that matters to you, their wings are sewn in NY. About on par cost wise with Deep Sea Supply, quality is about the same, but they are very popular/based in Florida, have a much more diverse dealer network than the others, and are high quality rigs. They were the first to market with STA's the CEO actually invented it, I think the backplate was first commercialized by them as well. Think Mercedes.
So is the Mercedes the highest quality of the lot, probably not, but at that point you are splitting hairs, so you can't really go wrong if you want a quality US made product at a reasonable price.
Webbing and hardware are all about the same, the first three probably have nicer finished plates than the others, they all make BEAUTIFUL backplates, but it's still a 6lb plate of stainless steel.... The wings are all splitting hairs as well, so it depends on who you want to support, what you want to spend, and which dealer you like the best..... Dive Gear Express is a great Dive Rite dealer in the general south Florida region, DSS and Oxycheq you'll likely have to buy sight unseen, Halcyon it is worth the drive to High Springs if you're wanting to see their gear, Extreme Exposure is a great shop.
Edit: Stuart, plates are all functionally identical but certain fit and features make some better than others. Halcyon, Oxycheq, and Deep Sea Supply have some of the most beautiful plates that have been made, they take a lot of time polishing them and it shows. Most of the others are machine polished and they're good enough, quite good in fact, but if you hold a Hollis plate next to a Halcyon or an Oxycheq it really is a night and day difference in overall quality. You can do the finishing yourself if you want, but the plates coming out of Florida are truly beautiful.