I don't know if my opinion on that topic really matters, since I never won a fancy 1v1 tournament and was mostly active between 2012 and 2015 so all the new "superstars" won't know me, I really think that fastest is a good balance between reaction time in terms of blocking and movement/ your positioning in a groupfighting line with your teammates. Back in times they created MM with the same melee speed as Native. Players were able to block in an enormously fast way and all these things like "blockchambers, stunchambers" etc. weren't a thing. You just needed your reactiontime to block and to chamber. Standing close to a player, you just had to react faster to chamber. With the creation of NW, the melee speed is slower as it was back in MM or Native. By slowing it down, many bugs and glitches came to the game such as "double x" and even the "blockchambers" which are not intended by the creators. Pokes and stunns are very common nowadays. In contrast to MM, you have to focus much more on your movement in order to not get stunned by an enemy to further block other enemies. It is not possible anymore to just run in the enemy line and block everything, you might have the right reaction time, but you are most likey to be stunned. For me that's the big difference between MM and NW. It's just two different metas. Changing the melee speed to fastest, you increase your ability to block more often, since stunns don't affect you that hard, but you are still stunned and have to watch for your movements. Of course spamming is a big thing with fastest, but blocking twice in a row as in Native is the way to counter it. In a 2v1 situation you rely much more on your blockings skills and I personally think that's much more fun to play. Random stunns don't appear that often. Fastest, as I wrote before, is a good balance between the individual skill in blocking and the individual movement skill and teamplay. It combines the MM and NW meta, and I really like it and it's actually confusing why we have this discussion in 2018 and not in 2015 or 2016