IMO you have to have an ipad in this industry whether you like it or not. Every app that exists comes in iOS form. My ipad 3 only ever gets used at jobsites. I have no personal want/need for it because my smart phone handles almost everything and my laptop or desktop picks up where it leaves off.

Go with the wi-fi only 9.7" $329 ipad. All of our phones are hotspots now so its not important to get one with mobile provider built in. If you only use it for work and keep a case on it you shouldn't have to buy a new one for 3 or 4 years.