Would the Nazgul have been greater in power if they had their rings?

JRR Tolkien stated that Sauron kept the rings originally given to the Nazgul so he still had control of their wills.

"Who still through their nine rings (which he held) had primary control of their wills....."

From the letters of J.R.R TOLKIEN #246

So is it likely the Nazgul would have been even greater in power if Sauron didn't withhold their rings?