Hey Scott,
I haven't had the Whirlaway long enough to make a judgement call on whats better, but I have noticed some differences with the high speed model -vs- the ISE.
The Whirlaway has a noisier motor, but seems to handle some things more smoothly. I made home made chicken soup last weekend, and all the trimmings/peelings from carrots, celery, ect plus a lemon half were fed down pretty fast. My ISE would always THUD and CLUNK with the lemon rind, the Whirlaway did not. I also stuffed it full of chicken bones when Fred and Joe were here for New Years, and the bones were gone lightening fast!
The downside is the guard doesen't muffle the noise as well as ISE's does, a small trade off. I need to feed this thing some corn cobs and see how it does with that.
If you go for a Waste King, get a custom series model with the 3 bolt mount, much nicer than the plastic EZ mount on the Gourmet series.