Ok, so this review will have spoilers. I will do a super short summary where I will keep out the spoilers, then a full review where there could be some minor spoilers.
Super short with no spoilers: both are PG-13 and I would not recommend for any kids (quite a bit of violence and a little bit of language), but both get positive reviews from me for the age-appropriate audience. I'm not liking the Marvel trend of crude butt humor. I'm not a fan of romance and neither of these movies had much of that, so that was nice. I like light-hearted characters and both movies had these. I went in with too high of hopes for Thor and too low of hopes for Justice League.
Thor 3: I went in with high hopes for this one - it's Marvel; it's not GotG; it's classic characters Thor and Hulk and Loki. I was a little disappointed but overall still give this one a positive review. The negative is that Disney/Marvel is really on the butt humor trend that GotG2 started but thankfully was not nearly as crude (still kinda crude though). The positive is that it has some good humorous points, there is no romance, and Thor is just a really optimistic character.
Justice League: I went in with low hopes for this one - BvS really dampened my hopes for a DC movie and I just didn't see this matching up to WW. The good news is, they stayed off the crude humor trend, there is minimal romance, and added some really optimistic characters (Aquaman and Flash) which strayed away from the dark doom and gloom of MoS and BvS. I give this one a positive review. The scene with Aquaman and the lasso of truth was hilarious.