I hate online dating and yet I'm at the point where I wouldn't date any other way, probably.
When I date people I've met in person I think the thing that lays the foundation for that relationship is lust. I like the look of them, they like the look of me, we get talking. But I know almost nothing about them at that point and it's so easy for them to hide who they really are by just dodging subjects etc., things I don't find out to be obstacles until way later. Some people worry about people online pretending to be someone they're not but it always amazes me that they ignore how much easier that is to do in person.
Online people openly list things like their political views, their favourite TV shows, music etc., long before you would find these things out about them in person. Especially on OKCupid, with its question format, it's super easy for me to, for example, click right through to the disagreement section and eliminate anyone who doesn't answer "yes" to "are you a feminist". Because honestly it gets tiring for me to have to educate good looking arseholes on these issues IRL.
The last time I agreed to a date with someone I met IRL I just got super skeeved out and cancelled last minute. I realised I didn't know anything about this person and for example if they were to chop me up and murder me, no one would know where I was because he could've given me a fake name, a fake job title, everything. If I meet someone from the internet I snap some details of that person's digital footprint and make sure my sister has all the details of where I'm going to be and what time to call to make sure I'm home and safe.
It feels safer overall though knowing I have a 99% match with them on issues pertaining to how likely they are to respect my bodily autonomy, how entitled they feel to sex, etc.
This is surely different if you meet someone via law school, or if the environment you grew up holds similar values to the ones you now hold as an adult. But if you wasted those years on a bad relationship or ended up having nothing in common as an adult with all your early school friends, online is a good place to find that special someone to suit a weird duck like you.
tl;dr key difference: in person you meet someone and slowly get to know them, online you get to know someone first and then decide if to meet them.