Back to the original question.

In the heli muffler food chain, here's the ones available.

Muffler: allows for reliable performance albeit at the expense of top end power. Most quiet option for helicopters.

Tuned Pipe: allows for best power output from engine. However, the "tuned" means you have to set the length of the header precisely to correspond to the power band set for your engine. If you don't do it right, you will not get the expected results. Plus, these things are longer so most require you support the pipe properly and securely.

Tuned Mufflers: are a hybrid of sorts, they allow for good power (less than a tuned pipe), but not at the expense of poor idle to midrange engine performance which is typical of tuned pipes.

So, it really boils down to you... reliability or power. There's always a trade off. For learning, reliability is the best, the last thing you want is a flameout during the learning stage.

For power, tuned pipe is the way to go. This is true more so for some european flyers who use low to no nitro fuel (nitro is expensive in most European countries) to squeeze performance out of their engines using straight fuel.

In Asia, tuned mufflers maybe preferred as nitro fuel isn't as expensive as in Europe, but our weather conditions make it hard to run tuned pipes as the temperature varies greatly during the day with extremely high humidity.

As for R50 choices, the Weston is ok, but the one-piece variety tends to break at the header joint more often than models using a silicon joiner.

Hope this helps.