I used to do inline skating as my main sport, and completed the 87-mile Athens-to-Atlanta race 4 times. DNF'ed once due to a blister. (APRR Chuck, I assume this is the 87-mile race of which you speak?)
Anyway, after I had my son, I just couldn't get out on skates any more. The logistics of driving out of the city to train and then driving back just didn't fit with an infant at home. So, I thought I'd try something new and take up running. I figured that the discipline of training for an endurance event would be similar no matter what the sport.
It turns out that I am a FAR better runner than I was ever a skater. I was always a back-of-the-packer on skates, but in my first running race (6 weeks after starting to run), I was smack-dab in the middle of the pack. And 6 months later, I ran my first marathon and BQ'ed.
I loved skating. I adored my teammates and the camaraderie. I did the Eddy Matzger workshop every single year and practiced the drills in between. But I still sucked at it! My transition to running really made me realize that some people are simply built to for certain sports, and that no matter how hard you train, it may be impossible to excel in some others.
So, I have a hard time comparing these sports personally, because I just find them so different with respect to the degree of exertion. I worked hard at inline skating, but with far less gain. As for injuries, though, I can say with certainty that I suffered through far more traumatic injuries on skates, but I've struggled more with soft tissue injuries from running. I don't know if that's just because I'm getting older, though (45 years old). I've never cycled competitively, but I did complete a century ride once with my DH and loved it.