I like the tone of both. For strictly performance gains, the gains are going to be minimal with a catback alone and there hasn't been any side to side tests.
The Megan OE-RS should offer gains with having slightly larger piping. For best exhaust results would recommend upgrading to a jpipe and test pipe as well for most performance out of the exhaust.
What are your goals performance wise? For strictly performance probably are some other areas to focus as well like pulley, UR spacer and gaskets, ported intake runners, etc.
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