BlackBerry Messenger
If there's one thing that BBM has over iMessage is that it has incredible depth. It's simply dense with features, and has its own separate application that's usually preinstalled on the BlackBerry. It's very much like other instant-messaging services where you can add contacts and create groups. Indeed, sending out a broadcast message to a group via BBM is
how the London riots were organized. Group communications isn't limited to just messages either -- you can share photos, lists, calendars, and chats within a BBM group. It's also a little like Facebook and Twitter, where you can update your status, change your profile avatar, and let your friends know what song you're listening to.
If you don't have the app already, you need to create a BlackBerry ID along with a password in order to download BBM from BlackBerry App World if you have BlackBerry OS 7 (EDIT: We erroneously said you needed an ID to use it, but that's only in the case of OS 7). Once you have the app, you have a few ways to add your friends as contacts. You can e-mail them a request along with your PIN, which is a number that ties your ID to your BlackBerry. If you already know your friend's PIN, you can enter it into the BBM app and request contact that way. If your contact is in your address book already, that person's contact name will appear in BBM. Another option is to use the phone's camera to scan someone's personal BlackBerry bar code if he or she happens to be next to you. You can also send BBM invitation via text message, but that might incur texting charges. Bear in mind that regardless of how you add your contact, that person has to approve you before you can start exchanging messages.
When sending messages, you can ask for a read receipt, and you can see your contact typing a response in real time. You can also "Ping contact" to cause your friend's device to vibrate. But if the recipient has the "Ping contact" vibrate option turned off, that won't work. Like with other instant-messaging services, you can set your status display to available, away, or when you're busy. As you might expect, BBM supports multimedia messages as well, like pictures and video. BBM is currently integrated with many social networks, like Facebook, Twitter, and more. The latest version of BBM, BBM 6, now lets developers create apps with the BBM API. Developers can create apps that let you share information with other BBM owners, like games and social apps like Foursquare.
BBM has many more features and settings, like no character limit, the ability to change how your contact's name appears on the list, and you can sort chats chronologically or alphabetically. BBM and RIM's network is also known for encryption and security,
though as we've seen lately, it's not always so reliable.
iMessage
Apple's iMessage doesn't have nearly as many features as BBM, which in turn makes it a cleaner experience and easier to understand. You still need a log-in and password--that would be your Apple ID--but you likely would have already set that up when you were setting up your phone, so you don't need to re-enter those credentials to use iMessage. Additionally, iMessage utilizes the
iPhone's existing Messaging app, so there's no need to download and configure another application. There is not much of a learning curve--if you know how to text with iOS, you already know how to use iMessage.
There's no real need to request contacts for iMessage as well. As you're entering the recipient's name or number into the To field in the Messaging app, it'll automatically detect that your recipient is a fellow iMessage user, and will automatically change that text message into an iMessage. It doesn't matter if the recipient is in your phone book, either; even if you're entering a person's phone number for the first time, it'll detect that you're sending an iMessage. The only time you might have to request someone's Apple ID is if he or she is using an iOS device that's not a phone, like an
iPad or an
iPod Touch, but even that's usually as easy as entering in an e-mail address.
Like BBM, iMessage has the option of sending you delivery and read receipts. You can also see the other person typing his or her reply in real time. A particularly cool feature is the ability to start your message on the iPad, for example, and finish it later on your iPhone. It has support for group chats, and has e-mail and FaceTime options in case you want to move the conversation away from iMessage. You can also send locations and contacts, but you need to do so from the Maps or Contacts app. With BlackBerry Messenger, you can share that information from BBM itself. For those who are worried about security, iMessage also promises end-to-end encryption for their messages.
BBM is for those who like the multitude of features and settings that complexity brings. However, it has quite a barrier to entry. It uses a separate app, and with that, a completely separate ecosystem from normal text messaging. You have to request contacts to be added to your list, and there are a number of ways to be added: e-mail, PIN, or bar code scanning. iMessage, on the other hand, is built into the existing messaging structure. You won't even know you're sending an iMessage until the phone automatically detects that your recipient has it, too. The barrier to entry is thus extremely low; if you know how to text, you know how to iMessage. iMessage can also be used across all iOS devices and not just the phone; you can start a message on one and finish it on another.
In the end, it boils down to whether you're a BlackBerry person or an iPhone person, and which phone most of your friends use. But if you had to choose, it would be BBM if you prefer a feature dense application with a longer history and more entrenched fan base, and iMessage if you prefer a seamless experience that anyone can understand.