Sorry for the delay in getting back to you, Doug/Bedifferent. I am the original crash test dummy for many of these alternative tire choice, but I've had no direct experience with the Avon Cobras, the most expensive option that I'm aware of. Mind you, that all of my personal experimentation has been been on Mulberry Mistress, an '07 Standard model.
The B'stone Max is, generally speaking, the best option, at present, as a rear tire for our Rocket IIIs. depending on your riding style and local road surface composition and condition, it will give you approximately 10-30% better lifespan (mileage), it slightly improve your geometry and it will virtually eliminate the speedometer deviation inherent with the Metzeler rear, at least that is the case for all non-tourer models. I now have a matched set of Exedra Max's front and rear, however I'm running a 130 up front and
it's most important to note that anything smaller than a 140 in front on any R3 with ABS brakes and likely on non-ABS Roadsters is dangerous as the smaller section width will cause the ABS to be non-functioning and the lowered front geometry can cause bits to drag that potentially cause the bike to become ground-hooked and cause the rider an unintended, grievous accident.
That said, I'm a big fan of smaller front tires for two reasons. first they will make the bike feel a good 100 to 200lbs lighter and secondly, your turn-in will be quicker and easier, your tracking will be vastly improved and those attributes combined with the lighter feel equals more and better feedback and response both to and from the rider, less rider fatigue and dramatically improved handling across the board.
The Michelin Commander II in a 140 size would be my recommendation for the front of your R3T for the aforementioned reasons. I believe that Jag is the first here to use matching Michelins front and rear on the R3T, so his feedback will be most informative for that set up. I can, however, tell you that the Commander II's tread pattern matches up very nicely with that of the Exedra Max and, IMO, properly maintained, unabused Michelins could very well deliver 10-20% more mileage than the EMAX, simply due to their use of Aramid cords. they also happen to be a great looking tire.
Also, I believe that the Michelins might feel a bit sticker that the B'stones toward the last 2/3 of their lifespans, as the rear EMax does tend to lose more of its surefootedness in the last 25% of its safe tread life, which is about 8,000 miles maximum for this aggressive bronco buster, than does the OEM Metz.
