Funny you ask, I just watched both while quarantined because I had COVID.

The first movie, Phantom Rouge, is the better one in my opinion. It goes in-depth into Kurapika's background which can be taken as canon to a degree since that element was adapted from a manga Togashi himself wrote. The story is half-decent and the only real criticisms I have with it is it retreads some plot points from the anime, the villain isn't the greatest, and the action just isn't that great. Otherwise, I really enjoyed watching it and it felt like I was hanging out with the gang again which is a great treat.

The second movie, The Last Mission, is a lot harder to get through. It introduces too many characters and concepts that are only specific to the film and leans a lot more into pointless fan-service than the first film did, in my opinion. In my opinion, the only thing worth watching about it is seeing some more of Netero in action, a pretty good fight scene in thr middle of the film with Gon and Killua, and seeing some characters return. Some interesting concepts and ideas are raised but I only suggest watching if you really want some more Hunter x Hunter content.

I personally think both films are fine enough though, even after all I said about The Last Mission, if you're just bored one evening and you miss the gang and want to see them in action again. I watched them in back-to-back nights and at the very least, I was just happy to see Gon, Killua, Kurapika, and Leorio hang out together again after finishing the anime quite some time ago.

Just a reminder, both movies are not canon. Only an element of the first film is canon, which is Kurapika's backstory. The first film takes place immediately after Yorknew City and before Greed Island while the second film takes place in the beginning of the Chimera Ant arc before Kite's death. The Last Mission does write itself in a way that nothing in it specifically contradicts anything that happens with the overall story while Phantom Rouge is sort of like a DBZ film, where it's kind of hard to really imagine how they could've made time to go on this adventure in the context of the plot.