power will be the same, they are both a straight through muffler but the packs are louder and poppier. I love my regular magnaflows and o/r h its still insanely loud at WOT
I love my magnaflows. Upr offroad X with magnaflows welded up to Bassani piping [ame=http://vimeo.com/5559460]Magnaflow on Vimeo[/ame]
My bassani's were trashed so instead of a new complete catback, I just cut the bassani's off and welded in the magnaflows
Here is a quick breakdown for you. Performance will be the same because they have the exact same straight through core.
Sound-
Talking 03-04 Cobra specific. An oval Magnaflow and Magnapack will be about the same which is why on the 03-04 Cobra, there is no separate Magnapack cat-back system. This is because on the oval mufflers in the Cobra system are offset/offset on the same side for the inlet and outlet. So you aren't getting as much sound suppression you would with a same size muffler with a center/center in/out. Hope that makes sense
MagnaFlows are very tame with stock H-Pipe, I had them for a couple of years and then swapped out the Magna Muffs for some FlowMaster Super 40s and couldn't be happier. However I heard the MagnaPaks on an 02GT with stock mid pipe and it sounded so MEAN! Totally diff sound then my Magna CB on my Cobra. I don't know if the Magna Paks sound diff on a GT vs a Cobra but the MagnaPaks were way more aggressive in my opinion.
i like the sound of the magnapacks IMO....and for power i would have to go with the magnapacks also just because its a circle canister and its a straight shot.
I have headers and x-pipe with magnaflows and its not real noticeable at idle but at WOT they sound awesome with no drone. My buddy has the same setup with magnapacks and its a pretty noticeable at idle and at cruising speed over the magnaflows and has a little drone. IMO I like not having all the noise at cruising speed and no drone, but the loudness when it opens up. As far as performance im sure they are the same.