A simple solution that would for you to give me the invite.  You system is up and running, right?  Don't rock the boat.  I am in the queue for a 3070 with no end in sight.  Hmm, is it easy to under clock a card?  Just get a larger power supply, right? ;)
 
Yea, I know, it is what everyone is thinking.  I just thought I would say it loud to break the tension. 

Are you an overclocking enthusiast?
 
That's the question.
 
If you "just" want a super premium 3090 that can run at very good overclocks stick with the Strix. 
 
If you want to break records or score personal bests and have a card that can run aggressive overclocks as a daily driver get the Kingpin.
 
The Strix 3090 is better than the EVGA FTW3 3090, but it's not as good as the EVGA KP 3090. So it depends on what you're trying to do.
 
I'd say most 3090 buyers are not super budget concerned. If that's you and you want the best then the 3090 Kingpin is it. If you want functionality because you run multiple 4K monitors or a high end VR setup, then the Strix is your ticket unless you also like extreme overclocking to get you that extra bit. 

undecided65
Yeah, I wasnt planning on overclocking. I would stick it at the highest possible 'stock' setting though. I am assuming that the KP will be quieter/cooler than the Strix.

Yes, my Kingpin which hasn't properly been deployed to my main PC since I need to get a water block for it is performing at better efficiency, by a lot, than my 3090 FTW3 that is similarly deployed. Runs cooler, uses less power, has better results.
 
I have a friend who has a Strix 3090 so I could ask for comparable metrics since they are all performing a similar task ATM but since he hasn't mentioned significantly better efficiency I assume he isn't getting it, since we regularly compare notes on such issues. 

If you are interested in any srt of competitive overclocking, get the Kingpin 3090.  The strix takes a lot more soldering of extra stuff to the PCB to get anywhere near the level of voltage control that the 3090 KP has.