Magnaflow or Dynomax Ultra Flo? Or something else?

The three mufflers I'm looking at are:

Magnaflow, 18-inch long, 5X8 oval, S/S,
Magnaflow, 24-inch long, 5x8 oval, aluminized ( frown )
Ultra Flo, 20-inch long, 4.25x9.75, S/S

I have MSDS headers, no cats, and this will be the only muffler in the system. It will be located where the stock resonator was.

2000 Mercury Cougar V6 ATX. 16.0@87MPH, 155.0 FWHP