balloon sizes and their significance

So as I work and design this game, something I'm finding is that balloons seem to have the most utility at size 2-3, in situations where you need a big balloon, a size 2-3 that can be inflated to that size on the same turn or a later turn just has better flexibility than a size 5 balloon. Size (should) matter a lot in this game, bigger balloons can swing into spent balloons and trade safely, and bigger balloons can dodge spot removal and be more resilient.

A size 2 that can reach any size has high flexibility. so then when should a balloon be larger than 2?