One-on-one SMS was mostly fine, but group SMS was a constantly-buggy mess back when I was on Android, too.
I wouldn’t be surprised if SMS experience has more to do with carriers and with the details of the network topology and composition between correspondents, than with phone vendor.
There's no such thing as group SMS. Your phone either sends multiple SMS messages, or uses something else than SMS (usually MMS). I'm talking about SMS specifically, as CSM chunks aren't relevant to anything else.
My assumption is that iOS somehow manages to lose some SMS messages when sent in rapid succession more often than it would happen for usual reasons.
I wouldn’t be surprised if SMS experience has more to do with carriers and with the details of the network topology and composition between correspondents, than with phone vendor.