Turtledove, he has a slightly better grasp of butterflies and plausibility, not that's saying much.
"butterflies and plausibility" I said "writer", not "alternate history writer"
No contest. Stirling by a landslide. His characters speak like real people, his narratives are efficiently done, he doesn't jump between dozens of redundant PoV characters, but focuses on only a few that are key to the story. As a writer, his worst is far better than the best Turtledove
I also think his true alternate histories (the Draka books and Peshawar Lancers) are more sweepingly "alternate" than most recent Turtledove. On the other hand HT's alternate histories seem generally more plausible and grounded in at least some relevant historical research. But bottom line, if I am looking for a good read to kill some time and I have a choice of two unfamiliar AH books from Stirling and Turtledove, I'll always grab the Stirling.
Fully agree with you on that pointYou should try to read some of Turtledove's early stuff (aka his stories from Analog in the 80s). It's pretty good. (Though there's stuff on this forum that's definitely better)
I think Turtledove's problem is that he actually should be a short story writer and not a novelist.