I recently bought a Vandoren Optimum ligature for my tenor, to go with the V12 mouthpiece I had also bought, and was very impressed by it. It was a significant upgrade from the Rico ligature I had been using. I therefore decided to order one for my alto as well. This turned out to be a completely different story.
I have a Yanagisawa AWO2 and am using a Meyer 5M and the supplied Yanagisawa ligature with Select Jazz 2H reeds. The Vandoren sounds very good with all three plates. It has a sweet, singing, lively sound and I have no complaints about it at all. It's just that the Yanagisawa is better. The Yanagisawa gives a stronger, fuller core tone and works better for jazz, which is what I play. in comparison, the Vandoren lacks depth but is smoother and sweeter, especially at the low end.
It may be that the Optimum ligature in combination with a V12 mouthpiece would work better that the Yanagisawa - they do seem to be a very good match on my tenor - but I tried the V12 on my alto and didn't like it as much as the Meyer, so I didn't go down that route..