Normally, removing the baffle increases the top end power at the expense of noise, idle smoothness and transition/mid-range (possible dead sticks). I do NOT recommend you trying this as a beginner or if you are not confident of a safe landing in the event of a random engine quit.
Advantages/disadvantages of exhaust alterations are all dependent on any given combination variables of engine model, prop load, fuel, glow plug, set-up and flying style. Change one thing and you could have an entirely different beast....good or bad. That's what half the fun is in this hobby, experimentation, but be sure you are up to that step first.

You can sometimes find a shortcuts by asking what's working on a specific engine. Give lots of details, plane, prop, glow plug, fuel brand-nitro-oil , current rpm, muffler(baffled?) desired results, flying style.

I've been hearing a lot of good stuff about Mac's new "high volume" one piece black muffler#6720 for the 55AX.