Having run several of the mentioned tires at one time or another I'll chime in with a couple data points. Sorry if it's turned into a book!
Bear in mind I'm an autocrosser. I spend as much time as possible in slip angle. It's what weekends are for!
I had several sets of Sumi HTRZ-2's on my 99 Cobra, liked them a lot wet or dry. Very sensitive to air pressure - run recommended pressures and they're docile, cushy even. Not crisp turn in but quiet for 3/4 of their life and very good in the wet (these were 245s, the 275s seem similar but the 315s are different). Aired up and not-too-much heat they worked very nicely. For those that don't know the company (I didn't), at the time they owned Dunlop and cross licensed manufacturing with Goodyear (meaning most US Sumis were made by GY and most Euro/JP GYs were made by Sumi).
On the same Cobra I went through many sets of Kumho Ecsta MXs, which are the predecessor to the XS. This tire loved heat and all the abuse you can throw at them but would go square sitting overnight, and were very greasy for the first 500 miles until you wore off the mold release agents. Conclusion seems to hold true for the XS as well, again much air and almost as much heat as a race tire. OK in the wet down to about 1/2 tread, got noisy then too.
Ran a couple sets of Nitto 555R2 in drag radial and non-drag radial. Nice enough street tire with softer compound, worked reasonably cold to mild heat. In reality they're neither fish (street tire) nor fowl (race tire).. I kept them around for early spring/late fall events when you knew you weren't going to get enough heat in the slicks and/or you saw enough wet to be "beyond a sheen". Not sure about the non-R compound, guess I'd expect it to be slower and more forgiving than the XS. Note these turn square after sitting a few days too. 5 minutes (or more air) fixes that.
The GS-D3s were OEM on the 03/04 Cobras, many of the guys I ran with liked them well enough (and they got high marks for wet) but they pretty much all migrated to faster & cheaper tires after a set or two.
FWIW the new hotness in street tire autocrossing amounts to Toyo R1R and Dunlop Star Spec, I've not looked to see which are available in 275 & 315.
On our Z I really only run Hoosiers so can't say so much about c4 street manners, the rim protectors I use are just to get back/forth between shops/inspection and distant events
. But I found with all the tires I've used "in anger" they all prefer different pressures, temperatures, and alignment tweaks to get the best out of them. For street with weather and novice event work I'd save the $ get the Sumis and remember a little cheapie compressor for track stuff. Next choice for the same duty would probably be the 555s, the later Nitto NTs don't have enough sipe for weather IMHO.
PS none of the above performance tires are worth a tinker's damn below about 50 degrees. Also it does not take much mileage with abuse or alignment issues to wear a tire into behaving badly - I had to get religion about rotation and flipping on the wheels. I'll guess that could have been a part of 4-cam's Sumi problems. And I should note that it's taken me 10 years of multiple sets a year and much experimentation to learn what the dynamics are telling me a tire needs in terms of alignment/pressure etc and even then it's successive approximation.
I should also throw in that the OEM alignment specs for C4 are hideous and the performance difference to be found in just that is profound. Of course I should add that if anyone tried to transport either of our c4s (88 z51, 91ZR-1) on a worn-in road with our event setups they would pronounce them undrivable in 1/2 mile or less - keeps you alert!
Thinking back to the 70s, all these tires are freaking amazing. YMMV!
Cheers,
- Jeff