Which one is stronger? I have an Atlas I NOT Atlas II. I want to run it with 44" meats, Big Block, and a 4500LB rig. Will the Atlas I be OK or should I use the 205? Anyone use an Atlas I?

Depends on gears mostly. 205 is overall going to be stronger but crappy low. I hear the lower gears that are available in the atlas make them weaker and not good to put behind a big motor.
That said if your geared right in the diffs and not the real low gear set in the Atlas then your probably going to be ok. Well unless your running a 502 through it. Then you might want to start thinking Doubler for the strenght.

run hte 205 (if iin good shape) sell hte atlas

I have seen about a dozen of those atlas break..with far less than 44's

Where did you see the Atlas' usually break at? Is there a weak spot on these cases? Mine is the Atlas I 3.5 ratio.