Karune shared details of the Reaper vs. Hellions’ effectiveness against enemy units and the differences between both units in certain combat scenarios.
Karune: The Hellion is faster than the Reaper side by side, but the cliff traversing talent often gets the Reaper to the place you want to go faster.
In raiding, it really depends. Hellions will be able to hit several workers at the same time, but Reapers have much more direct damage. Choosing what to use may also depend on what you are up against. Hellions are armored, whereas Reapers are light armor. Both are very useful for raiding and used in conjunction effectively could easily mean GG quite early, bleeding the enemy economy and tech.