I've picked NL up last week after becoming weary of the slow updates NH is getting, and becoming curious when lurking a bit in forums (due to my disappointment with the last NH update), with many NL players praising the game.
So far (after 1 week only though) I find NL to be much closer to Wild World in overall feeling and design, and I gave WW a decent chance but didn't play it as much back then as I've been playing NH during the past year. So I really have no nostalgic feelings towards earlier entries of the series too. The design and UI of NL have a lot of quirks that are difficult to return to if you are coming from the, in comparison, extremely polished New Horizons. In NL, you can't try different outfits with various colour options at the Able Sisters (and the clothing, including your own designed one doesn't look as good too), villagers can move out if you don't return regularly (which is stressful), you have a really tiny inventory with very limited stacking (and you have to stack fruits manually one by one), and you have to use the touch screen all the time, which breaks gameplay flow. I couldn’t buy a new fishing rod for days because it appears randomly in the shop. It overall feels more grindy. Fossils collection is slow because randomly gyroids (which have no use..) and traps will appear.
There are huge limitations in what you can customize outside your house. I realized that the creativity and self expression that NH allows were actually very important to me. The museum is just a shade of what they made of it in NH, and I did not feel the wish to visit it late at night so far (which I often did in NH, nights at the museum are cool). I don't think that the dialogue with the villagers is more interesting than in NH yet, but maybe it will become better with time. The home visits and the errands for the villagers have felt rather boring and superfluous to me.
Still, I already understand those who would like to have NLs content back in NH. The game indeed gives you the feeling of living in a small town from the beginning. I already found a number of things that should have been in NH from the beginning, e.g. actual information boards at the museum (I wish I could read some trivia about the exhibits during visits, at the moment only the art gallery has this..). Maybe I will change my opinion in the next weeks. But so far I think NH is the much better game by comparison, but lacking several functions and content from NL that it really should have by now.
I think NH is brilliant in that they went full into providing the most stress-free and relaxing experience possible. They seem to have removed everything that could cause even the smallest amount of discomfort. Although I'm usually not a graphics enthusiast, I found that the smooth, adorable, beautiful and detailed NH graphics (and the optional TV mode) contribute a lot to its relaxation effect. I can't even play NL without turning 3D on because the graphics look so dated, even for its release date. I've had to think "3D was a mistake" (Playstation 1 era) several times.
I think Nintendo has been following an 'identify, focus and double down on the most important elements' strategy with the development of the Switch, and many other games like AC, and their current success is due to this. They don't provide menu themes, StreetPass and other gimmicks in order to have resources to focus on the actual games, and not waste energy on maintenance of nice-to-have-but-unessential functions. For NH they fully went into the idea of AC being a series of sandbox games. And this worked out very well, I love exploring what people came up with during dreams and on the web. I often get back into designing my island when spotting a neat little idea somewhere.
IMHO a New 3DS (if you can get hold of one) is worth picking up nevertheless. I got it for the N64 Zelda remakes, but it has an amazing library. It collected some dust after I got my Switch though, so definitely check out whether there are other exclusives (DS & 3DS libraries) that are interesting to you first, and don't get it for NL alone.
@MyDanes: Doesn't NH save automatically? I found NLs manual saving quite annoying, especially after getting Resetti only because my battery ran out.