I was 17 yrs, 7 months but I skipped a grade. It would have been nice to be held back if only to not look like I was 13 most of high school - that's not a big thing with the ladies. I grew about 4 inches and put on 30 pounds in about the last 6 months of my 17th year - that would have been nice for sports too.
Definitely something to factor in when it comes to sports. If a 17 year old senior is only slightly behind the 19 year old, take the 17 year old.
Note that Teasdale will turn 19 in late Oct of his senior year.
It would have been pretty cool to "legally" drink early in my Soph year of college