I like to have one of each on my team, but if I absolutely have to pick between the two, Id go engineer, at least until the Recoiless rifle upgrade. I like engineers because I know exactly where the grenade will go, and, if sapper is picked, what terrain will most likely be damaged.

Rocketeers are fun however for those “fuck it” moments, when you need to deal a lot of damage to a large number of nearby enemies. The wide explosion radius also helps a lot with the native tile spread they have.

Which to you prefer?