Based on the anecdotal reports on this forum and others, Sailun S637 tires are quite competitve with Goodyear G614, and typically at a much lower price.
There is an important difference however. Goodyear, for the G614 and selected other tires, has a Damage Policy. If a G614 failure causes damage to your RV, Goodyear, by policy, pays for repairs.
In 2014, we had a 4 year old G614 (40,000 miles) throw off its tread, causing body damage. Goodyear paid for roadside delivery and installation of a replacement tire and also paid about $2,200 for body work on the RV.
I'm not aware of Sailun or any other tire company paying for body damage repair. And paying the cost of roadside replacement and installation ($550) on a tire that's 4 years old with 40,000 miles is also pretty unusual.
Note that this is Goodyear policy, not warranty. That means they could change their policy without notice.
Nevertheless, Sailun makes a good tire at a good price.