I would consider Wormhole to be the best powerup in Present Rush. It can be a game-changer especially if you get it in a location where there's lots of uncollected fuel. The workshop teleporter is also great, as you can travel further from your workshop and collect a bit more fuel without worrying about how slow you'll be for the return journey. Those two powerups along with the speed boost are the ones I usually aim for, and I think most of the others are not really worth going out of your way to get.
Decoy is my favourite powerup for Snowman Survival. Obviously, being able to turn invisible in a game where the objective is to find/catch you can be pretty useful. I like to place it in a hidden area to get the most use out of it, but it can also be used to confuse the snowmen for a few seconds if you're being chased right at that moment, and you might get away. Also, the stabber - you should get medals from using them on snowmen so it's always worth grabbing one and hunting down a snowman if you're able to.
