I agree that either is going to work fine. Fire stick also can control the TV power and volume, and depending on the model, has voice control built into the remote. Not something I use very often, but my kids do.
The higher tier Roku products have these features too. I also like that the Roku remote has a headphone jack and comes with earbuds so you can listen to it with the TV muted if you're trying to be quiet in your house.