Being in the middle of a Good to BB migration, here are my thoughts.
With Good, there is always the case of 2 sets of everything. Native contacts, and Good contacts. Same with Email, Calendars, Tasks and Notes. With BB, everything is native. Advantage, BB
Good will take over the phone limiting use of voice dialing and custom themes, among other features. Advantage, BB
When moving a message in Outlook, from your Exchange mailbox to a PST, the message will stay in the BB mailbox on your phone. Advantage, Good.
Slingplayer mobile will only work on a limited number of BlackBerry's (no Sprint or Verizon models). Advantage, Good
The phones just work
Advantage, BB
All kidding aside, the phones just seem more intuitive. We had people on Treo's and Moto Q's, and about 95% of the users I have moved, LOVE their new BlackBerrys. The noly model we're using is the Curve, so I can't say what any of the others would be like.
Hope this helps!
Tim