I'm surprised nobody else has chimed in here.
Advantage would be, if it works that way, everything going through the sump goes through the skimmer. I don't believe it works that way, although some will disagree with me.
The disadvantage is you may be losing out on some flow if you downsize your return pump to match your skimmer pump.
I would recommend getting the biggest, best skimmer you can fit in your sump. Then aim for about 8-10x turnover through the sump. Too much flow can cause noise and bubble issues.