It's hard to say which is the case, though. In 2012, CNN's final poll of Florida found Obama leading by 6 with RVs while Romney was up 1 with LVs; Obama wound up winning by less than 1 percent, suggesting the LV model was closer to the mark. But in Colorado, the RVs had Obama ahead 8 while the LVs put him up just 2. Obama carried Colorado by more than 5 points, so there, the two voter screens split the difference.
If we have more of a Florida situation here, then Cotton either has a slim lead or the race is tied. But if things look more like Colorado, that would mean Pryor's the one in front. In a way, it all makes perfect sense, since the two have regularly swapped leads in the polls. CNN's Janus-faced numbers just confirm that this race is indeed a tossup.
10:26 AM PT: P.S. Steve Singiser compared RV and LV results for the final set of national polls in 2012. In every case, the RVs were closer to the mark than the LVs. And in 2004 and 2008, RV polls were also generally more accurate than LV polls.