I used a Cozmo from 2007 until 2011 when the warranty expired. I switched to a Ping, which I've been using for almost a year now.
It's funny because the slow bolus delivery on the Cozmo used to drive me CRAZY. I used to disconnect for a workout or shower and it would be so annoying having to wait for the bolus to deliver for 30 seconds before I could disconnect. With the Ping I just bolus and disconnect in two seconds.
I love the display on the Ping. I can actually read it with a magnifier. I'm visually impaired and I'm not able to read any other pump even with a magnifier. That reason alone will keep me an Animas customer unless other companies start adding high-constrast displays.
The feature I miss most on the Cozmo is definitely the site change reminders. I also liked that you could change I:C ratios in smaller increments than you can on the Ping. On the Cozmo it's also possible to change the reminders and the temporary basal rates in smaller increments than on the Ping. I miss all that. (It's kind of ironic because the Ping makes a big deal about how it has smaller basal increments than other pumps, yet every other setting is more restricted with larger increments than other pumps, or at least the Cozmo.)
Ergonomically, I much prefer the Ping. Fits much more nicely into my pocket or clipped to my belt.
I also love the meter connection to the pump. I love being able to bolus on transit or somewhere else when my pump is buried under layers of clothing and not easily accessible. I do with the meter allowed you to do a few other things, like set temporary basal rates, though.
I was using the Cozmo 1700 and never did upgrade to the 1800 (they didn't handle that very well in Canada), so I didn't get a lot of the fancy, newer features or I'm sure I'd have missed some of them.