I think it's mostly subjective or anecdotal, but what comes to mind:

• The community generally is more friendly. Absolutely, there are still jerks or trolls around, but the ratio of jerks or trolls feel way less than reddit.
• I feel more active here myself. This one I can't explain. The community is smaller, so maybe I'm not subconsciously worrying about being drowned out by other comments? On Reddit, I'd average about 1 comment a month at best. On here I usually leave a few comments a week.
• This point might not mean much if you didn't join reddit when it was younger: I joined reddit when it was still young. I think back in '08? Lemmy feels like a young reddit, back when I enjoyed it most. Again, I can't really explain this since it's just a feeling, but one example of what I mean by "young reddit" is community wide memes. Wayyyyyy back in the day, everyone on Reddit was ravaging about "The narwhal bacons at night" or something like that lol. There were also a bunch of dickbutt memes.. if you know, you know. Well, my first week on Lemmy everyone was posting beans for a good couple of days. No reason. Just beans. A few weeks ago there were a bunch of "Taylor Swift going to Australia," Taylor Swift taking a swim," "Taylor Swift spotted at the airport," titled posts, but all those posts were pictures of airplanes. The rotating meme right now I think is Jeans??? Idk. This is just a symptom of a younger community, and why I like it more, but there's more to enjoy about it than rotating memes. This place just feels more genuine as opposed to artificial if that makes any sense.
• I feel like I'm not missing out on anything on Reddit and I have a healthier relationship with social media on this site than with reddit. Every once and a while, I log back onto Reddit to see what's going on. Most of the "Big news" that's posted on there is also posted here, but the experience now feels more bloated compared to here so I don't stick around as long. As for this site... Yes there is less content. Yes there is less to scroll through. At the same time though, you can scroll for a very long time if you really want to. This eventually led to me being on my phone less and being somewhat a little more productive as opposed to doom scrolling.
• Lemmy absolutely has better third party support for well, anything. Sure, it doesn't have official apps, but go to the app store and count how many different Lemmy apps there are vs reddit. Nearly all of these apps are better than the reddit app IMO. Most of these apps are also FOSS; they're free with no ads. Yes, there are still few paid apps as well if that tickles your fancy. I know Sync for Reddit came over to Lemmy as Sync for Lemmy as an example. This shouldn't stop at apps though. I wouldn't be surprised if there are browser plugins.
• You have more say in your experience here. Again, with the smaller community, your voice is louder. On top of that, is your server's admin doing something you do not support? Your instance is doing something you don't like? Create an account on other instances! Lemmy is federated, so most of what you see should be the same as in other instances, but you aren't under the rule of one toxic CEO anymore. I myself have like 4 accounts on 4 different instances lol.
• Piggy-backing off of the previous point: if reddit is down, it is down. If your instance is down here? Sign into another instance!
• On the opposite end of the spectrum, does some instance have a bunch of members or just communities you don't want to see? Lemmy might not have native tools out of the box, but some Lemmy apps will let you block entire communities.
• One fun thing I like about Lemmy is you can post pictures in comments!

If anything, the only reason why I still use reddit is for smaller, niche, communities. To that end, yeah Lemmy is smaller, thus the smaller reddit communities are even smaller here. If I find myself wanting to make a post on a given niche topic, I typically post on Reddit AND here. Sometimes, my post on Lemmy will somehow get more comments than reddit still though. Reddit posts seem to fall off after a day or so, that's not typically the case for Lemmy if you do trend something.

At the end of the day though, this is just a social media platform, and the enjoyment you get out of it comes down to you. ☺️ One tip I do have though is to sort by "Top of 6h" or "12h". I don't like the "Hot" sorting on here that much.

I don't think this is definitively "better" than reddit. The functionality of the site is more bare bones. No big hidden features or anything like that. What you see is what you get as far as interfaces go. But I am enjoying it. It reminds me of a much younger Internet and much simpler times. I am loving that Lemmy servers are run by your average joe who just wanted to start up a Lemmy community. No single CEO who only cares about how profitable a site is.