There is no advantage one way or the other, as both methods produce the same result—a parallel connection that delivers the same amount of power to each speaker enclosure (given that your enclosures have the same impedance). For the sake of simplicity, we generally recommend connecting each enclosure directly to the speaker outputs on the amplifier.
* SWR amplifiers that fall into this category include: 350x™, 550x™, 750x™, Baby Blue Head™, Workingman's® 2004, Workingman's 4004, Workingman's 8004, WorkingPro™ 700, WorkingPro 400, Bass 350™, Basic 350™, Studio 220™ and SS 180™