If you only had to choose between the YS or the OS engine, then I would go with the OS too.
Granted the YS engine will way outperform the OS engine, but unless you are experienced in getting them adjusted, you will have problems. Folks have been rebuilding the YS fuel pumps a lot on them too. That isn't to say you have to do it a lot, but eventually it needs servicing. Basiclly if you have problems and the engine was running OK before, and the valve gaps are set OK, then the fuel pump needs servicing.