The green bubble means iPhones have downgraded the conversation to SMS, or MMS for group chats. It results in lower quality attachments being sent, and fails to implement some nice features that would be available with RCS - like typing indicators, read receipts, and emoji reacts.
iPhone users expect these features through iMessage, but don't realize that the features are missing from green message chats due to Apple's stubbornness to avoid implementing open standards, not due to anything in particular the Android device is doing wrong. I'm not saying RCS is the end-all be-all, but any kind of shared protocol that Apple had worked to develop in good faith would have resulted in a better experience for iPhone users. So it's really disappointing that the only the option they give their users is old school SMS.
Pardon me, but I thought we were talking about the green/blue messages on iPhone, not the overall usability of iPhone vs Android. Let's stay on-topic here.
iPhone users expect these features through iMessage, but don't realize that the features are missing from green message chats due to Apple's stubbornness to avoid implementing open standards, not due to anything in particular the Android device is doing wrong. I'm not saying RCS is the end-all be-all, but any kind of shared protocol that Apple had worked to develop in good faith would have resulted in a better experience for iPhone users. So it's really disappointing that the only the option they give their users is old school SMS.