I do like the new one better. The old one was a 213 "segment"^[The first 54 episodes may contain multiple segments per episode, akin to something like spongebob] adaptation of a 34 volume manga. Still, the old one uses traditional animation styles which gives its its own charm, and it's more cartoony and looney than the new one is. The new one has better pacing, better animation quality^[From a "standard" modern perspective], and the OP and ED are both phenomenal.

Apparently the manga has more plot progression though, which sorta makes me curious to check that out. Being completely episodic is kinda frustrating when I do actually want to see the main character change.

That said, I like the series, I like and feel for Lum, but I'm not much a fan of the MC - you're not supposed to be tbh. At best he's an asshole, and at worst, he's unfortunate due in part to his own foolhardy assholish decisions.