I have the Ion which i got mid last season for 25% off at Dicks ($375).
Its made by Eskimo, and will accept any strikemaster brand auger. I have personally had a Lazer and Mora on mine.
Last season i was able to punch 80 (yes 80) holes thru 13in of ice with my 6in mora and still had battery left.
The Gator has a higher RPM, so it will cut faster than the Ion. In the video linked you can see it punches through the ice 4 seconds after the Gator.
If weight is a concern, the Gator is roughly 8-10lbs more than the Ion depending on the auger. With my 6in mora on mine it weighs exactly 20lbs. Thats the same weight as just the head of the Gator.
Customer Service is another concern for many. There have been alot of negative reports about Gator customer Service.
When i got my Ion the battery was faulty, Eskimo had me a new one within a week.
Price is also in favor of the Ion. If you already have a quality hand auger (Lazer, Nils, Finbore) they are pretty close in price (499 vs 539). However if u have to purchase a hand auger the Gator jumps quite a bit. As the Ion is sold in large chain stores, you can also wait to get the on sale as I did at 25% off, making is $375 vs 539. Which is a substantial difference to me.
In the end all your getting with the Gator vs the Ion is speed. The trade off for that speed is; heavier, more expensive, bad customer service.