The short, quick answer is that they are similar because both boost power.

Tuned pipes can be "tuned" for a particular prop/rpm, thus you can produce more power if done correct. One disadvantage is they are bigger. Tuned mufflers are tuned at a particular rpm so you have to prop accordingly to get max power. The advantage is they are smaller.

As for the Evolution blue muffler, they say that its tuned for 15k+ (website says at or above 15k). That is why I am asking playntraffic how his setup performed (Evo 60NX with Evo blue muffler). I want to know how much (if any) of a boost he is getting over stock muffler. I believe he is running in the 13k range on a 11x6/7 apc prop. I'm thinking about trying this muffler on my Mag 52.

I have a more detailed information on tuned mufflers, so pm me if you want to know more.