I also have one of each and I agree with the above comments. The primary difference IMO are the necks. The RSD neck is maple and is thinner back to front, very similar IMO to the neck on my Fender Player P, which I quite like. The Sado is a fatter, rounder, roasted maple. At first I was a bit offput at the thicker neck but it didn't take long to get completely comfortable with it and it's my primary go-to now.
I bought my '23 Sado branded one first and owned/played it for several months before acquiring the RSD. Some may recall there were some posts about a reseller (Franklin Guitar Works) that had bought a bunch of the returned RSD's and simply separated the necks and bodies, both loaded with all tuners, pickups etc still attached and in tact, and auctioned them off in mass on (if memory serves ) Ebay. Anyway I bid on and won both a loaded body and loaded neck and put them together for $370 total. I keep it as a backup and occasionally gig and rehearse with it. Required some adjustments and tweaking to get it up and playable but once I got it dialed in it setup, plays, AND sounds as good as the '23. If you're on a budget and are looking for the Sadowski tone and playability they're definitely a workable option.