As a contributing writer, Chibnall wrote "42," "The Hungry Earth/Cold Blood," "Dinosaurs on a Spaceship," and "The Power of Three." Middle-of-the-pack episodes, nothing awful but nothing really memorable either. Certainly Chibnall never delivered anything like the stuff Moffat wrote during the RTD era.
I also agree that Moffat's best work was as a contributor under RTD. No surprise there, the demands on the lead writer/showrunner are exponentially greater. But that means, if you're going to pick your showrunner based on their skill as a writer, they better be a really damn good writer. If somebody was merely competent as a contributing writer, they're not up to wearing the big hat.
Anyway, back to Davies: I'm very happy with RTD coming back. By all accounts, he has continued to hone his writing skills in the ten years since he left; and he has the experience of having run "Doctor Who" before, so he won't have to learn the ropes the way a new guy would. Plus, he's had ten years to reflect on what worked and what didn't during his first run. I don't think his second run will be just a retread of the Ninth/Tenth Doctor era. And if it is... well, that was a pretty good era, there are worse things to make a retread of.
Also, Davies handpicked Moffat to take the reins after him, and Moffat delivered. So when the time comes for RTD to move on again, I have hope that he will do an equally good job choosing a successor*.
*Though I will have to call shenanigans if he picks Moffat again.