I have Titans (OEM) on my 6530, 10 years and just passed 1000 hrs. Rears are 16.9x28 6 ply, forget fronts but are 10 ply big and fat, front and rears are F1 bias. Very little wear. The front shows thin rows of slight, shallow cracks around the start of the lugs but been that way since new. Rears show no cracking at all. It's 65 PTO 4wd and I'm pulling implements I had bought for, and used with, my JD 4230 2wd 100 hp PTO tractor so I guess I'm getting good traction.
I chose to dump the R4 rears on my 2400 and needed a match for a 12x16.5 R4 6 ply. Surfing I found that Titan was the only supplier to have a match for that in a turf: 33x12.5x16.5 4 ply. Local sell anything 5th generation tire store is also a Titan dealer, picked them up for less than half of list price (about $600 each, got for $260 ea.) and by waiting for one of his normal tire delivery trucks got them with free shipping and no tax since for ag use. Can't beat that.
Not a Titan fan. Just stating facts as they pertain to me. For the last 15 years at least have been running Kelly Springfield Powermark 2000 16.9x28 4 ply R4s on my 2000 and 3000 Fords (same sets on each) and they have been great running/lasting also. Ran other brands on other tractors over the years including Firestone and Good Year and can't site one over the other.