Whilst my iPhone 5s is way better for reading than my Garmin Edge 800, its still too frustratingly small.
I've just grabbed a secondhand iPad Mini 3 cellular for an improved big picture mapping experience.
The latest firmware allows me to add a memory card reader so I can add the pics easily from my dslr which was a deal breaker for my purchase decision.
I was tempted by the iPhone 6s+ but at the end of the day, price wise and screen realestate wise, I'm happy with my decision.
The 64gb iPhone 6s+ is very dear here in Australia at $1379.00 compared to my iPad purchase.
Definitely a bit lighter and less bulky than my Macbook air to haul in a pannier.
Reminds me, I've yet to try for size in my handlebar bag.

I bought the lightning to SD Card Camera Reader at a half price sale from local store "Officeworks".
http://www.apple.com/au/shop/product...eader?fnode=85
Works a treat for both my iPhone and iPad Mini