I've had a Dainese (too hot), old style over-armour and a 661 Turtle suit.
I was fairly happy with the turtle suit until I forgot it and went trail-riding without any armour - I hated the lack of protection, but the increased mobility and decreased heat makes the probability of crashing that much lower (yes, seriously). And its a bit crap with the Leatt brace, despite supposedly being designed to work with it.
I've gone back to the old armour but feel a bit unprotected, particularly on my lower spine. Plus I f%^king hate seperate elbow guards.
My current thought is to use the turtle suit for MX and colder-weather trail-rides, and only use the over-armour for warmer trail-rides/enduros. It's kind of the opposite to what most people do, but it seems like the right answer to me.