So Im replaying Mass Effect 2 and I've played as every class except for Engineer and Sentinel. So which one should I choose and why?

I went sentinel it's a hell of a powerful class my shield power was in the 800 range making it a tank class so to speak.( If going sentinel tank build)  What sentinel lacks is fire power So Have some one with you who can do massive damage.

Some help with sentinel class builds here.

http://masseffect.wikia.com/wiki/Sentinel_Guide_(Mass_Effect_2)

doesn't matter which ever abilities you like more

I played as an Engineer and found it to be an intriguing experience due to the Combat Drone; however, an Engineer's usefulness during some missions is lowered due to dependency on enemies that have tech abilities or are synthetic. Sentinels have a beefy defense and are versatile, though lack weapon options at first. Either is fine, but Engineer is more for manipulating the battlefield at a distance while a Sentinel can get up close and personal.

I'm playing my first Insanity runthrough as a Sentinel. It is good fun.

I haven't played as Engineer yet, but it does not seem like it would be as frenetic.

Sentinel. Sentinel's have high defense and are more versatile. You have power options in for either organic or synethic enemies. Engineer's are interesting but I don't like most of my abilities being useless against anything that isn't a geth or mech.

Sentinel is the only class I like to use in Mass effect 2. Easy to use and good defense and abilities make up for the  lack of weaponry.  Mordin and Miranda are always in my team. 

Mass effect 1: I liked both Soldier and Sentinel classes. I tried the other classes but they were not for me.