Too many variables to do a real comparison. Age difference, technology difference, userbase difference, administration difference.
Reddit used to be great, and that's why a lot of us are here now. It's not a problem with the technology or userbase (mostly, though past a certain point the popularity can become a detriment). It comes down to the administration, which I think is the only thing Lemmy has got over reddit right now, but it is a major thing.
For me as an older user of reddit, and older overall lol, I'm enjoying it here better. Less bullshit to scroll through and so far people here seem more polite overall. When I first joined reddit I'd have likely joined here too. I had previously joined digg and a few others.