I've used them all except the copper 8055. I've also had Oyaide 046, 004, and 079 and the Furutech FI 25. I used them on Sunny Cables P600 power cords and later on DIY cable from Mundorf and some very nice vintage silver plate solid core copper wire.
Let me start by saying I'm not terribly fond of gold plugs or outlets as they obscure detail and roll the top end and usually fatten the bottom as well. I did prefer the IeGO 8085 gold to the Furutech FI 25 as it did less of these offenses. Of course some would argue that the Furutech was the warmer, fuller bodied plug. That will depend on your personal preferences.
The IeGO 8075, rhodium over copper plug, is a pretty good all around plug that does everything well but is nothing special. At its price point, its competent. I might have a better opinion of this plug if I didn't have the IeGO 8095 and the Oyaide 004 and 046 in my systems.
My preference is for a highly detailed and focused sound. I like pinpoint imaging when possible and tight tuneful (textured) bass. I want to hear as much as possible without the sound being aggressive. To that end, the three just mentioned are all fine choices though the 004 can be bright in the wrong application. The 046 takes a bit of edge off compared to the 004 and may be a slight bit less detailed though still excellent in my opinion.
Comparably priced to the Oyaide plugs, the IeGO 8095 is a favorite of mine. Detail is equal to the 046 and probably closer to the 004 but I've never compared directly so …… Where I think the 8095 might be the best plug is in the top end. It has more sparkle than the Oyaide plugs but does so, not only without brightness, but actually smooths the aggressive tendencies that my system sometimes exhibits. Using these IeGO plugs with Mundorf gold/silver wire, I don't find myself experiencing the listener fatigue that plagued me using most after market power cords. (Fusion Audio Enchanters, BMI Whale Elite, Whale Supreme, Hammerhead Gold & Shark i, Gutwire Power Clef and a lot of others I can't recall).
I forgot to mention the silver plug. It's also competent at its price point but again, nothing I'd get excited about compared to the 3 I listed above. Of course you need to find worthy cable to add these plugs to or you're just wasting money.