There has been a general consensus that, when it comes to Windows tablets for business, those running Windows 8 Professional are the most appropriate choice. There are many reasons for that from a security point of view: Windows 8 Pro supports enterprise level security technologies such as EFS and BitLocker, and can be managed as a member of a Windows domain. But Brien Posey says you shouldn’t automatically dismiss Windows RT:
http://uk.enterpriseefficiency.com/author.asp?section_id=2725&doc_id=259507
Of course, assuming you’re deploying company-owned devices rather than engaging in BYOD, substituting RT tablets for Intel-based ones, at least for certain users, can save the company money – but there are security advantages, too. Because it runs on ARM instead of x86/x64, RT is not vulnerable to malware written for the latter platforms, and because its desktop is locked down and doesn’t allow installation of legacy software, and the apps in the Microsoft Store are vetted, users can’t get into trouble downloading and installing malicious programs.
As for usability, my own experience with RT led me to the surprising conclusion that you can actually get a lot of work done with the device:
http://www.techrepublic.com/blog/tablets/hands-on-getting-real-work-done-with-surface-rt/2855