I managed a guitar store fron 1977- 1988. We were an authorized dealer for Gibson, Fender, Guild, Yamaha, Ovation, Takamine, Washburn, etc. We did a lot of maintenance and repair work and were part of the Ax-In-Hand chain in Illinois. Larry, the owner of Ax-In-Hand in DeKalb, IL was one of the first well known and knowledgable collector stores. For example, for years he had a wall of SGs- one example of every model for every year from 1960 or whenever they started that shape through 1969. So, an SG Jr, Special, Deluxe, Custom for every year. And that wall was only the part of the SG collection. He had similar collections of all sorts of acoustic arch-tops, flat-tops, arch-top electrics, semi-hollow electrics, etc. So I got the opportunity to have my hands on a LOT of Gibson ES-33X guitars. And I was a huge fan of an ES-335 because of a photo of Clapton in the Blind Faith days sitting on a blond Fendery piggyback amp playing his 335. Plus Alvin Lee, B. B. King, Freddie King, Elvin Bishop, then later Larry Carlton and Lee Ritenour.
So my take is this- The SF-IV is much more consistenlty well made. Some Gibsons are indeed special guitars but too many are at best mediocre. Every SF-IV and the two SF-V I've played are on par with the best 335s and exceed the two 345's and 355's I've played. I read a Larry Carlton interview decades ago (when he still had long hair...) where he talked of the differences between Gibson and Yamaha. This would have been around the time they had the SA-2000 out. He said if you took 10 new Gibsons and 10 new Yamahas, all 10 of the Yamahas would be excellent guitars. But while 7 or 8 of the Gibsons would be only mediocre or worse, and 1 or 2 would be very good, there was the likelyhood that one Gibson would be exquisite and special. I'm not sure the same comaprison will hold up with Guild, but I've never played a SF-IV that made me say "Eh, not good". So there's the consistency of each instrument which is really helpful if you can't get your hands on one to play it before you buy it. I wouldn't take my chances on a Gibson without having it in my hands first, but would on a Starfire.