The 900 is also a great engine in my eyes... in fact I've always been an advocate for it here... your right in saying the 900 and 700 are the same engine... but the 700 did not share the crankshaft issuses that the 900 did, and I'll also add that it was mostly the 2005 model of the 900 that was scrutanized so bad.. the 06 900 was leaps and bounds better but it already had a bad rep.
The crankshaft in fact was very durable in the 700 due to the fact of less vibration and horsepower than the 900. Yes it still vibrated some but not as bas as the 900 which also I don't find that bad. With lower stress on a crank designed for a bigger displacment engine makes for a very tough combonation. Most of the "speed problems" that some 900's and 700's had was not due to bad engine performance but bad clutching. These motors make their power much lower in the rpm range that most other motors. The clutches were wound too tight with not enough weight in them to shift properly.
I'd love to have a '06 700 Fusion with a torque arm and push arm, SLP pipe & can, SLP airbox, and a ECU flash. Just by doing that you save 32lbs over stock which makes it lighter than a XCSP 700, IQ suspension, and you bump it to 146hp with 101 lbs of torque in a reliable 7600-7800 rpm.