Quoted from Nokoro:
I’m going to have to choose one to do before the other. I’m leaning towards House of the Dragon, but that’s more of an HBO bias than anything about the shows.
I watched the first episode of Rings of Power, solid production values but a little slow moving and they picked some odd looking actors for key elves (I'm looking at you Elrond -- more aloof and ethereal and less Keebler, please). I'll watch it all at some point but it's not actively drawing me back. That said I came in with an attitude problem (why mess with the beloved canon?) so the show would probably have to be a home run to overcome that.
I'm caught up on House of Dragons, the first episode was great, there've been some solid eps since but also a fair number of dull or implausible scenes. So halfway into the first season I'd say still interesting, but not as griping as the original series. But I'll keep watching as the new episodes drop (there's apparently a time jump mid-season so we're all about to meet new actors playing some of the key characters, which could be great or disastrous).
Of the two I'd recommend House of Dragons, but know that it's not perfect and will have trouble measuring up to OG GOT (as would most shows, of course).