When comparing iMessage vs Reach, the Slant community recommends iMessage for most people. In the question“What are the best messaging apps for iOS?” iMessage is ranked 5th while Reach is ranked 29th.
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 Mass message multiple people at once
Ability to send a single message to multiple people without exposing their contact information to each other. Reach sends individual messages to the group rather than starts a group chat.
Pro Personalized and Individual conversations in "Group Mode"
When sending a message to a group of people, Reach starts a private conversation in your Messages, Mail or WhatsApp apps respectively for each recipient
Pro Reusable Recipient Groups
Improve workflow productivity by creating reusable recipient groups
Pro All platforms in one: iMessage, Text/SMS, E-mail, WhatsApp, and Google Voice
Reach does not require the recipient to have Reach installed on their device. Instead it uses the existing messaging apps on the device to send the message to the recipient.
Pro Message Templates Feature
Prepare message templates which can be reused. Message templates can have recipients name variable, for example the template "hey {first name}!" will be populated with the recipients first name when the message is sent out
Pro Free texting through Google Voice
Reach integrates with Google Voice and allows to send free text messages in the U.S.A and low rates across the globe
Pro Fully automated mass texting with free SMS
Using Google Voice integration, Reach is able to send mass texts in a fully automated mode (without the need to press "Send" button for each message)
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 Need to press "Send" button per each recipient
When sending a message to a group, the user must press "Send" button for each recipient. The only work around is to use Google Voice integration for fully automatic mass texting
