For the same cost and slightly more base damage (but not health) than a Swarm Green Bloon, Double Red Bloon is more vulnerable to damage but is better with health-boosting effects that don't increase delay, such as Fortify, Zany Juice, and Zee Jay's Passive Awesomeness.
The cheapness of Double Red makes it an especially good candidate for Zany Juice in the early-game to apply quick pressure.
In Aggro, Double Red is subpar in a deck compared to Yellow Bloons and all of their variants, as well as normal Green Bloons, but versus decks without a cheap answer it can be useful with Zee Jay when played very early.