Yesterday I took ownership of an ipad pro 9.7 to replace my ipad air, the only reason for me doing this was i got frustrated continually running out of space on my air and my data contract had run to the end of it's course, the air 1 imo is a lovely device and it's my wife's new ipad (only used for a few games and web browsing so 16Gb is enough for her) prior to that I had the ipad 4, and it's still running really well. In terms of use iPad air1 to pro the screen is lovely and the smart keyboard and pencil additions are useful split screen multi-tasking is great - forgot about that nugget until playing around, but all in all they are really similar in most respects, yes it's faster and (possibly more memory) and the camera is better, for day to day browsing watching videos etc.
As an aside I was offered the 2017 ipad for a few £ per month less than the pro, I couldn't really justify it, it seems to me that if you need to get a new ipad and are looking at a cost effective option go for the 2017, if you want more features, thinner, lighter, better processor, the ability to use the pencil and smart keyboard, better camera and video recording and better speakers the pro is the option for you.