It's no secret that today's soldiers train on all manner of video game-style simulators. In the United Kingdom's Ministry of Defense, British servicemen use Virtual Battlepace 2 as part of their regimen. VBS2 is a product of Bohemia Interactive, who also made the first Operation Flashpoint game and now produce the ultra-realistic ArmA shooter sims for the consumer market. (The U.S. Secret Service use VBS2, too.) However, unlike the OpFlash games, VBS2 hasn't gotten an update since 2007. In the dog years of video game engine iteration, that's a loooong time. With recruits already having experienced the better graphics and gameplay of Battlefield 3 and Modern Warfare 3, British military are finding that VBS2's hoary old experience no longer holds new trainees' attention. Bored soldiers-in-training probably aren't what you want to be sending all over the world.

Read more at: http://kotaku.com/5871848/the-uks-ministry-of-defense-wants-simulators-as-good-as-battlefield-3-or-modern-warfare-3

Arma has a more realistic feel to it than either BF3 or mw3.
I'd love to play BF3 arma style in a slow methodical way but it allways seems to be played at a RUSH.
I'm not sure that playing BF3 would be anymore than a time filler for the troopers, certainly they wouldn't gain anything useful from the experience.