I have one page with my full history of text messages, full transcription of all voice messages, contacts information connected with every number, and I can search everything. I can configure which of my phones ring.

And, possibly most importantly to me right now, my current phone has only a data connection and I make and receive calls using the Voice app. I think SIP eats too much battery and data and doesn't work well for wifi<->lte switching, but it's been a long time since I used it much.