It seems like with the first option you could really elaborate a whole lot more than you could with your second option. Tearing your ACL and doing rehab/training for 6-7 months sounds like it impacted your life more (in regards to time and the effects it had on your mind/body, etc.) than one time you called for medical assistance for a drunk friend. And though you said you weren't drinking at the time, I would still question why you were underage and with someone who was also underage and so intoxicated. Ya know? I think the second one would just open up too many questions.
With the first option you can really highlight how you overcome obstacles when something bad directly affects you.