One of the main reasons I went with a 6 Plus (128gb) was to eliminate my need for and iPad altogether. I have found, however, that I still use an iPad frequently (at work, home, coffee shops, etc.). Now I'm thinking the 6 with an iPad is probably the better combo for me.
I'm curious how the Apple Watch will change my usage patterns. I can't imagine using all 3 other than at home maybe. I think it would be a little much to receive a notification on 3 devices.