Why BBM when there is Whatsapp?
Comparing BBM to Whatsapp is like comparing apples to oranges (whichever is apple or orange and whatever that means). Even though the instant messaging features are the same, they are simply not the same thing.
Whatsapp is tied to your number. I don't like this. Anyone with your number can just hit you up and that's it. (Yea, yeah, I know you can block and all that, but that's another layer of friction). I can't count the number of times I use Whatsapp for snooping. Call from an unfamiliar number? Number you stumbled on somewhere? Just add the number to your contact, refresh your Whatsapp contact list and view profile.
BBM answers this via the pin feature. I don't need to give you my number before we can chat.
And two, I hate that Whatsapp last seen feature. That's the real snitch there. On BBM I can ignore your chat by not opening the conversation thread. You don't get the R notification. On Whatsapp, last seen tells you I've been ignoring you and chatting with other people.
I got BBM yesterday and I see myself using it more. Eventually, I may even uninstall my Whatsapp. Whatsapp is a great platform. The cross support across different OS is just awesome. Personally, I think it's the best messaging platform out there. If you have Whatsapp, you really may not need BBM. But that's not an assumption to generalize. Take it or not, this BBM4All thing is a serious shit.