There are a number of tire tests that helped set the ranking, by Motorad and other sites. The more formal, comparative tests were given more weight in the ranking process than user reviews.
In some cases the same tire was reviewed in multiple tests, so this helped bridge the gap between tires being reviewed in one test but not another. Intermixed with these more formal tests are other tires that were not part of formal testing.
The Pirelli Angel GT 2 is a replacement for the Pirelli Angel GT. In one multi tire test the Pirelli Angel GT 2 was rated highest. There are multiple reports of the tire following grooved concrete and causing the bike to feel loose. Some prefer the original GT to the GT 2. The GT 2 was rated tops primary based on tire tests. If you are concerned about road grooves then select another tire.
The Bridgestone Battlax Sport Touring T31 replaces the T30. This is more of a sport tire than touring tire. It sticks and handles well, and has lower mileage than some of the other sport touring options. Really the only complaint was mileage, otherwise riders praised the overall handling and feel of the tire. In a multi-tire test from Motociclismo, the Bridgestone Battlax T31 scored 8.5 out of 10, placing third behind the Pirelli Angel GT 2 and Metzeler Roadtec 01.
The Pirelli Angel GT is still a highly rated tire. Wet handling reviews are mixed. Dry handling is said to be better than the Michelin Pilot Road 3 which is another highly rated tire. The German magazine Motorrad rated the Pirelli Angel GT as number one in their testing. US-based reviews back up this high rating.
The Metzeler Roadtec Z8 Interact inspires confidence in stability, cornering, dry traction and wet traction. Tested on a variety of bikes and performed well on all of them. Especially impressed with handling with new front, worn rear. This will often introduce handling issues, but the reviewer still felt the tires delivered 90% of the handling performance. Others say the tire is better than the Bridgestone BT 021, Dunlop Roadsmart and Michelin Pilot Road 2s. Another likes the Z8 over the Z6.
The Bridgestone BT 023 has generally positive reviews. There have been various, formal tests of the BT 023. One reviewer rated the Bridgestone BT 023 4 of 5 stars, while the Pirelli Angel ST got 2.5 of 5 stars. A number of reviewers praised the stability of the rear in braking. Another feels the BT 021 turns-in better, but feels the 023 is more planted in the turns. Both wet and dry handling is praised.