I'm a fan of syncromesh. I used it in my old accord (1989)
It would grind everytime you put it in thrid. we changed it and filled it with synchromesh. it made an almost immediate difference. Within a few miles of driving, the grinding would only happen when you were "hot rodin'" it. Within a week, even that went away and it hasn't grinded since. and that was over a year ago.