Metlzer is a hard tire. Hence the reason it offers good longevity. But when I had my 97 and my 99 vmax at the same time, one had Shinko's and the other had Metlzer's.
The 97 I bought and the day I brought it home I took it for a spin and almost dumped it twice. Once from a dig, I launched it and it just spun the tire and went sideways. The other time I was rounding a corner and mid way through the corner I gave it some extra juice and it started to slide.
The 99 with Shinko's would NEVER do that. Hence the reason I almost dropped the 97 twice in one sitting. The tires don't compare.
So here is the bottom line, if you want to ride hard, then Shinko's is your choice. If you ride like a baby girl and want to look cool but not act cool, then buy Metlzers. Obviously I am joking here, but I think you get my point. The Metzlers are good tires if you want to do rolling burnouts and stuff and want a tire that lasts longer than 5000-6500 miles. They are almost twice the price of the Shinko's, so you will be paying the same amount roughly in tire replacement, just doing it more often.
Shinko pros
Extreme traction in almost all conditions
Cheap price
Nice looks
Good quality
Shinko Con's
Longevity suffers for traction ( I ll take traction any day )
Metlzer Pro's
Longevity ( at the sacrifice of traction )
Good looks
Good Quality
Metlzer Con's
Lack of hard core traction
Expensive
Bottom line in my opinion is the Shinko's offer more safety at harder riding situations. If you just cruise around, the Metlzer will suit you fine. But if you ride hard in the corners and out of the hole, then Shinko's will probably suit you better.