When comparing iMessage vs Pidgin, the Slant community recommends iMessage for most people. In the question“What are the best Skype alternatives?” iMessage is ranked 12th while Pidgin is ranked 15th.
Specs
Ranked in these QuestionsQuestion Ranking
Pros
Pro Secure end-to-end encryption
Pro Cross-platform within Apple ecosystem
iMessage is available on iPhone, iPod, iPad, and Mac.
Pro Supports voice messages
Short voice recordings/messages can be quickly sent, and messages can be easily dictated into written messages as well.
Pro Free and unlimited messages over Wi-Fi and data
Messages clearly indicates whether messages are being sent over iMessage (blue) or SMS (green) where messaging rates apply. iMessages do not count as SMS messages with your carrier, instead they use a negligible amount of data to send over Wi-Fi and cellular data networks.
Pro Clear indicators for message delivery and receipt
The app indicates when messages have been sent, when they have been read, and when someone is typing.
Pro Comes pre-installed
No need to download or sign up for a new service
Pro Seamlesss switching between SMS messages
Pro Friends don't need to "sign up"
You can just message them using their existing phone number or Apple ID and they will get your message.

Pro Clean UI
UI is minimalistic, and clear. And there is a plethora of stuff on the left of text box if you wanna use them.
Pro Apps and games for iMessage are available
For example, you can play games like pool or you can show someone a destination to go to .
Pro Support for a wide range of additional chat services
Pidgin not only supports IRC, it also supports plenty of other services such as AIM, Google Talk, MSN, ICQ and plenty of others. This way, you can have all of your conversations in the same app and won't have to deal with multiple chat windows being open.
Pro Free and open source
Pidgin and its code is completely free and open source. Pidgin has no ads and no features behind a paywall.
Pro Cross platform
The Pidgin instant messaging client is cross platform, working on Linux, Windows and OSX.
Pro Convenient notification features
Like other quality IRC clients, Pidgin features notifications that the user can set in order to have a variety of things happen when the users is mentioned, such as an audio cue or changing the system tray icon.
Pro Highly customisable with plugins
Pidgin not only has a large plugin library built-in, but also an array of third party plugins for a variety of functions.
Cons

Con Not cross-platform
iMessage is not available on anything but Apple devices.
Con iCloud sync of message is not stable
Sometimes, the messages on different devices with the same ID will be different, the syncing function work poorly.
Con Slow and unreliable
Con Miserable IRC font controls (as of 2.13.0.17)
Does its best to avoid putting sensible default font controls in any place where you can get to it. And when it does grudgingly change it, based on system preferences (not local preferences), it does so in an inconsistent and unpredictable fashion.
Con No native VoIP support
While there are plugins there is no built in support for VoIP in Pidgin which is time consuming to implement instead of being baked in from the jump.
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