Accuracy of Chess Engines?

How accurate are chess engines? or does each one more reflect the person who designed it? I feel like when i run games i've played through engines, different ones give different feed back on the moves that i made. Is this simply because multiple moves would have been better, or do they just reflect the belief of the person who designed it?

Depends. A good way to describe them is this:

They calculate ALOT. A few million positions each second. And then a little more. You should not try to outcalculate a computer (which plays on highest strengh)

However, they have some problems pressing in a drawish endgame. I doubt Anand would have lost the rook endgame in the 6. match game against a computer, since Carlsen didn't play the objectivly best moves. He played the moves which gave the highest chance of Anand to make a mistake.

I remember a Deep Fritz game against Kramnik from this position:

The computer didn't play f4, which is the most critical. However, in 99 out of 100 positions, it's much more accurate in the analysis than I am.