When comparing iMessage vs Line, the Slant community recommends iMessage for most people. In the question“What are the best messaging apps for iOS?” iMessage is ranked 5th while Line is ranked 9th.
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 Large celebrity and public figure usage rate
The caveat is that they are in Japan, but the app is commonly used to 'follow' public figures.
Pro Enormous, constantly updated stamp collection
Since many brands use stamps for promotional purposes, everything from movies to food brands to Taylor Swift have released stamp collections.
Pro Photo filter and editing capabilities
Users have in-app editing tools, as well as Line's separate camera application, which has additional tools.
Pro Integrated social network
Similar to Facebook's timeline.
Cons
Con Not cross-platform
iMessage is not available on anything but Apple devices.
Con Can't send separate texts to individuals who share a Contact record
iMessage is an utter disaster. It can't send separate texts to anyone who is on a shared Contact record but with separate mobile phone numbers (e.g., "Paul and Angie Smith"). It merges ALL threads that ever went to ANYONE on that shared Contact record. Want to text just the husband to set up a surprise party for the wife? Not possible. iMessage will ONLY add that new text to the EXISTING thread you had with the wife. Duh! iMessage is pitifully incompetent.
Con Blocking Spam Messages takes 3 steps more than is needed
You have to open the message, select the sender, open info on the sender, then block sender. The default Android message app, select the message, block sender. it automatically deletes the message and blocks the sender.
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 Account is locked to the Phone Number & Device
The entire account is locked to the phone number, which cannot be changed. If the application is installed on a new device with the same phone number, the previous account data will be wiped.
Con Users have been concentrated in Japan
Of the 360+ million registered users, the top country is Japan (50 million). Thailand and Indonesia are 2nd and 3rd with 33 and 30 million, respectively, with very small market penetration in the US (10 million, 11th place).