Comparing Michigan and OSU is interesting for how similar their 10-year averages are.
Each had one prolonged "golden era" (defined here by me as rolling 10-year average being a fixture of the 90+ percentile):
- Michigan's lasted 30 years, with the rolling average getting there beginning in the mid-1970s.
- OSU's is happening right now; it began after Tressel and likely has at least another decade of rolling average staying power
Each had one brief golden era:
- Michigan's rolling average got there in the late 1940s and dropped off after a half-decade
- OSU's rolling average got there in the late 1970s and dropped off after a half-decade
Each had one era ranking the the 60th percentile:
- Michigan's lasted roughly one decade from ~1960 to ~1970.
- OSU's lasted a few years in the late 1960s
Each had one era ranking the the 50th percentile:
- Michigan's lasted a few years in the 1910s
- OSU's lasted a few years around the late 1920s
I think you kinda brushed over the difference between Ohio State's and Michigan's lows.
Ohio State was below the 70th percentile for four years in the late 1960's while for Michigan I count 18. In addition to being more than 4x as long, Michigan's low was also worse bottoming out barely over the 60th percentile while Ohio State only barely fell below the 70th.
As far as the rankings below the 60th percentile I think you missed on the dates. Michigan's sub 60th percentile 10-year averages appear to be for the five ten year periods ending roughly in 1934-1938 not 1910's and Ohio State has four for the ten years ending in roughly 1928-1931.
The thing that always stands out about Ohio State is the remarkable consistency. A while back we were discussion Helmet status and
@ELA commented that one measure of helmet status to him is the ability to recover from a major drought and that it is impossible to evaluate Ohio State on this basis because they haven't had a major drought since before they ever were a helmet.
Looking at the 10-year average from Connelly that you posted, Ohio State started (I assume 1919-1928) in the mid 60's, dropped briefly into the high 50's then quickly climbed into the 80's even BEFORE Paul Brown was hired. Since they crossed into the 70's in the midst of the Great Depression (so ~80 years ago) Ohio State's 10-year average has only dropped below 70th percentile once, for four years in the mid-1960's right before going on an absolute tear that started with what Connelley noted as "Woody signs best recruiting class ever".
I'm not entirely positive from the context but I think that he meant "best ever period", not "best ever at Ohio State". The Super Sophomores of 1968 would have been 1967 recruits. In their three years playing they won an NC as Sophomores, missed it by one game (Michigan upset) as Juniors, and missed by one game again as Seniors (RoseBowl upset).
I don't mean this as a knock on Michigan or even a comparison to Michigan, I mean it as a comparison to every other school. I noted above that in the last ~80 years Ohio State's 10-year average has only been below 70th percentile once, for four years. Alabama's, for comparison, was below the 70th percentile for 21 years and below the 60th percentile for six years both right before the Bear. Michigan similarly spent about 20 years below the 70th percentile right before Bo and they also had another extended period below the 70th percentile including five years below the 60th percentile in the 30's.
It appears to me that Ohio State's worst 10 year stretch since the Great Depression was 1958-1967 which was completely within the Woody era and bookended by NC's in both 1957 and 1968.
Generally, Ohio State doesn't have the highs of the other helmets. Ohio State's best ever was a few years in the 70's during the Woody/Bo era and the recent past under Tressel and Meyer. Both of those appear to top out at about 95th percentile or lower. Michigan has three eras that at least match that (those ending in the late 1940's, mid 1970's, and the early 1990's) while Alabama has two periods that approach 100th percentile (one late in the Bear's tenure, the other now).
Most of the other "helmets" have higher highs than the Buckeyes but nobody has "higher lows".