So I checked out all three on Ike's site; the model number of the 200 and 160 matches the strobe intensity at full power (200 watt seconds, 160 watt seconds), the 125 is 110 watt seconds, angle of coverage is 100 deg, 90, 90, full power recycle times are 1.6 seconds, 1.5 and 1 second (I stand corrected). With regard to recycle, at the same watt second intensity the 200 is probably faster because it has a stronger battery. The 200 and 125 have TTL, full, half, 1/4 and 1/8 power settings; the 160 has TTL, full and 9 fractional power settings (in half steps?).
The SS200 was built for film cameras (Nikonus V, Motor Marine II, SLR's). Digital cameras are much more light sensitive, so it is very rare to need 200 watt seconds; I almost never use half power and use full power when subjects are over 10 feet away (which does have an effect contrary to guide # rules). Mostly I like the recycle time and wide coverage, but the 160 with the diffuser has the same coverage and similar recycle time.
If I was buying now I would get the 160, no matter the camera. My 200's have lasted through 4 cameras, and will work with whatever I get next (I don't TTL).