I think the main question will be: what next? Do the moors stay across the straits? Do the Byzantine holdings remain in place? Will there be a next wave (sometime in the 8th or 9th century, about the OTL invasions of Sicily and Crete)?
Visigothic Spain was not the stablest of places, but it was getting better at the time. The question is, how good will it get if the Arnulfing/Pippinid/Carolinigan Franks decide to do un-Christian things to their neighbours. Visigothic Spain may well play OTL's part of Lombard Italy. That is, of course, if the Pippinids don't get scotched by the absence of Saracens to defeat. But if push comes to shove, my money is on the Franks over the Visigoths.