I have seen both Trollhunters and 3Below, and I left a glowing review of Trollhunters (mainly of the villains)
3Below, I'm not ready to praise so highly,
The art style is beautiful as always, the character designs are pretty cool, and I enjoy the music. I LOVED the arch-baddie's voice and am sad there's not more of him. Some of the jokes are also quite amusing...at first.
It's fine for something bright and entertaining and whimsical.
Does this live up to Trollhunters, though? Not so much.
Unlike Trollhunters' villains, 3Below;s villains amount to mustache-twirling baddies at best, and incompetent excuses for action pieces at worst. The bounty hunters exist solely so that the good guys have someone to fight/acquire alien tech from when needed, and the senior baddie barely shows up at all other than to give his villain spiel about how he is Evil McEvilton come to overthrow a good, peaceful empire. In Trollhunters, the villains had a weight and menace to them due to the fact they presented a real threat to the Trollhunters, who struggled to stay ahead of them. In 3Below, the baddies are rarely seen, except when the plot needs them to show up, and they are not particularly intimidating despite the fact they are portrayed as though we should be frightened of them. They don't display much skill in fighting, despite the fact that they usually outnumber and outclass the heroes, and their plans and motivations don't reach past killing the heroes. Compare this to Trollhunters, where each of the villains was playing their own separate games trying to fulfill their own wishes and grudges (as well as racking up casualties on-screen and off-screen, making it much more believable that they can and would kill the Trollhunters).
The heroes themselves are okay, but they try to be funny too hard, and in doing so, the stale humor of "look at us, we're super-quirky" dialogue sweeps aside much room for character development, i.e. making the three into actually likable characters. Aja seems a bit selfish in dodging her duties for no apparent reason. Tech-guy (no, I don't remember his name even after 9 episodes) comes off as exactly that: he likes technology, and that's his character trait. Vex was funny at first, and there are some good scenes with him adapting to his human form, but he can get rather obnoxious. Even with episode 8's reveal, the viewer knows how Vex's character is going to play out and resolve this conflict. There is literally no payoff to this plot point: just set-up and instant reaction telling the viewer what they already know.
As far as the Trollhunters' appearances go; well, they're all right, but they only made me wish more and more I was watching Trollhunters instead of this. It's wonderful to hear the crew back together, and it makes me wish for more Trollhunters.
The Trollhunters world is better-built, their rules more concrete, the integration of both normal world and magical world much smoother, the conflict more intense, and the characters both more relatable and more exciting.
All in all, 3Below is a harmless, if slightly bland, addition to the Tales of Arcadia collection that honestly is a little lackluster after Trollhunters' magnificent storytelling.
I might pass on the rest of these episodes, but if you need me, I'll be re-bingeing Trollhunters for the third time!
(Seriously, just go check it out. It's TOTALLY worth it!)