I don't know where you heard that from, each time Michelin upgrade a tyre it has to match or exceed its predecessor in every category.
The Pilot Road 3's were the benchmark in wet weather grip and the 4's are at least as good if not better in that respect but last even longer.
I also go for longevity but still want a good handling and gripping tyre and prefer Michelins or Avons
I had a few e-mail exchanges with Tony Charlton concerning which tyres to put on my CB 500F, heres what he said
The Pilot Road is a single compound tyre, and though durable would offer slightly less mileage than the other tyres in the range, and doesn't benefit from having softer compounds on the sides of the tyre for better grip when cornering. The Pilot Road 2 and Pilot Road 3 are fairly evenly matched for tyre life, the big advantage of the Pilot Road 3 is it's better wet weather performance. The Pilot Road 4 builds on this, and according to our internal tests averages about 20% more life than the Pilot Road 3, so this should give you the best life.
In all seriousness though, the Pilot Road 3 has been the benchmark in wet weather grip since it came out, without any detriment to dry weather performance. When we develop a new tyre within a range it's key that the new tyre must be at least as good as the old tyre in all aspects, and improve upon it in the defined key areas that we've identified. For the Road 4 that has meant an improvement in dry weather handling, an increase in longevity and improving wet weather grip even further.
We generally look at all the competitor tyres and try to beat the best in each of it's strength areas to produce an all round top notch tyre. Every manufacturer moves the game on with each development of their tyres, so you really do get a good choice of quality tyres. Most specialise in one or two areas, and we consistently top the scores in independent tests on wet weather performance and braking, but we don't compromise on longevity in order to do that. We are still the only manufacturer able to create such a heavily siped tyre that lasts as well as anything else out there.
I hope that helps,
Kind regards,
Tony Charlton
Michelin 2 Wheel