The question I would ask you is what is the proposed use of the Tablets in the Field? Is it primarily to do meeting minutes, field reports, and be more accessible from the field? Transport and View Construction Documents, Specifications, Etc while on site? Is it a mixture of both?
If you are moving over to Google for everything an android tablet will be better and less costly; however today there arent as many relevant apps for Architects on Andriod as there are for the iPad. The iPad, in my opinion, has a better screen resolution which makes viewing construction drawings on site much easier as the screen size is larger. Google mail can work with either device pretty easily in my experience. The big question is cost for a firm your size the price differential for a WiFi only device could be $1600 - $2000 total to outfit an 8 person team.
I have used both and favor the iPad as the User Interface is very intuitive and there are many more apps. In addtion for the iPad there are some apps out there that let users compose mobile Field Reporting, Meeting Minutes, Contractor Reports, and view project documents.
Lastly, in regards to moving to the cloud I would say that it isnt something to be too worried about as many services are now delivered that way. Cloud Computing and Cloud Software usage is expanding and will continue to expand as internet bandwith increases. Our company delivers products over the cloud and we havent had a complaint to date.
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Caleb Morrow
Director of Sales & Marketing
ArchitTrek
Baton Rouge LA
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