When comparing Line vs QKSMS, the Slant community recommends QKSMS for most people. In the question“What are the best messaging apps for Android?” QKSMS is ranked 7th while Line is ranked 29th. The most important reason people chose QKSMS is:
When a new sms is received, a window will pop up that has the message and allows answering it from there, without having to open the app. It can be dismissed by tapping anywhere else on the screen.
Specs
Ranked in these QuestionsQuestion Ranking
Pros
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.
Pro Allows responding to SMS without opening the app
When a new sms is received, a window will pop up that has the message and allows answering it from there, without having to open the app. It can be dismissed by tapping anywhere else on the screen.

Pro Per-conversation notification settings
Users can set different notification settings per user as an easy way to know who is messaging without having to look at the actual message.

Pro Easily communicate with groups
Users can communicate with large groups at the same time due to the included group messaging feature. This is convenient when trying to synchronize with friends or colleagues.
Pro Very active developer who listens to the community
While QKSMS is one of the younger apps, the developer is quickly adding features/fixing bugs.
Pro Free
The app is available for free with an optional donation IAP that ranges from $1-$10.
Pro Beautiful design
Responsive, highly customizable Material Design interface makes for a native looking app that fits in well with Google's UI design guidelines.

Pro Save yourself from sending out bad messages
Through delayed messaging one can set it up so that a message is not sent automatically. This can help for those times that it may be best to think something over before sending out a rash message.
Pro Readable in day or night due to themes
There are light and dark themes available within the settings which can be switched depending on how light it is around one when using the app. The dark theme can also help to conserve battery when being used as not as much brightness and hence battery will be used.
Pro Schedule messages
Users can schedule messages to be sent for later.

Pro Convenient Android Wear support
Those that own an Android Wear device will be able to set it to receive their messages on the Android Wear device making for convenient notifications and easy messaging through not having to take their phone out.
Cons
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).
Con Last update was 2021
Con Buggy
There are little annoyances here and there, from dark theme problems making text unreadable to crashing and missing notifications.
Con Lacks features compared to other offerings
