You can't compare a N7 to a N4. Sure Jelly Bean is really nice, but is definitely not the same experience from the 2 devices.
First a tablet battery will last much longer than a mobile device. The N4 I used for a week was a pain to use because you had to micro mange the phone just in order to make it through a full day. Had to shut off features just to optimize the battery. Not something I was interested doing.
I enjoyed taking the N7 with me for my Thanksgiving getaway and didn't need to bring my MBA for the ride.
I found myself back with the iP5 after a full week using the N4. Def was a mistake. I find the iOS ecosystem (iCloud) for fluid than the Android ecosystem (Google Drive, Google+). However, the Android ecosystem wasn't bad at all.
Also Android is not leaps and bounds ahead of iOS
My opinion of course, and all user experiences will vary.
Sorry I meant more as example and introduction to android. They are different devices.
The leap and bounds argument is something not worth getting into on here as it useally turns into a feature check list. User experience and real world usage will vary by user.