So far from what I've seen there are 3 sentry bots.

1. A very tiny deployable turret. Not as powerful as the bigger one
2. A big deployable turret that seems to have more health and damage then the small deployable turret although is bigger an easier to target
3. A tiny deployable robot that shoots at enemy's while moving.

All of them seem pretty efficient and have there own strengths and weaknesses but which one is your favorite and why?

Mine is the tiny one that stays in place cause it's hard to see and hard for the AI to get a shot on it