Look again, there are still others. Get the case ported engine with an incorrect reed and you will have misery forever as some have found out.

As for the benefits, it's similar to the perception that many have where they thing auto advance ignitions are better than mechanical advance. They're not but people think they are so mechanical, which is less expensive and simpler, doesn't sell. Until you start using tuned exhaust systems most reed valve (or case ported) engines don't do any better than the standard piston port. But people think the reed engines are better so guess what they buy. If you ever have the opportunity to run some of the 50 through 100cc engines side by side of the two varieties you will be surprised to see some of the piston port engines performing better than some of the reed valve products. Brison is one of the higher performers in the original configurations.