I'd still say Ohio St has been more consistent. The last time they had back to back losing seasons was 1924.
The last time Oklahoma had back to back losing seasons was 1998.
Ohio St has never gone more than three seasons without finishing ranked. They've only had 3 total seasons where they weren't ranked at some point and only once have they gone more than a year without being Top 15.
So I'd still give the argument to Ohio St, but that's not a knock on Oklahoma. I will happily admit that Oklahoma is both one of the best and one of the most consistent programs out there. Where they're #1 or #2 or even #3 or (shudder) #5 in consistency, they're way up there and not likely to go through an extended rough patch, which I think supports your initial point