and I' 5' 10" with 34" inside and ride 20" Rocky Mountains of the early 1990's and that is perfect, no doubt about it, no matter what RobMac says.
I have an 18.5" Ricky and it's too small.
19/20" are the size I like to ride. I find many people ride too small a bike in my opinion.
The 20" Kona is fine also, easy and comfy to ride, a 19" would probably feel pretty similar just with a lower front end.
Rockies, like Kona's are measured Centre to Top if that matters
Each to their own preference and really, try and find out like most things.