Afair the frontal armor value of the X-Com overalls is 12, compare that with the hitting power of a standard-issue pistol (26) or a rifle (30). Here, we can't really tell what's 'realistic', but in-game this armor completely fails to protect against these weapons.
In real life, of course, even if an Interceptor armor can withstand repeated hits with 5.56 rounds, it hardly makes a soldier invincible - a bullet can hit in the face, or drill through an arm into one's chest... not even to mention that there's no such thing as non-lethal area when firearms are concerned, hits to the extremities being only *usually* non-lethal. And there's the issue of incapacitating shots that knock people unconscious - a rare sight in X-Com, that is, unless someone is beaten within an inch of their life. We probably need to compare statistics, as each point can be argued over and back again. I remember statistics gathered by the Israeli military, stating that the introduction of body armor increased survival rates of their soldiers by 30%. But the grander case is, how we can even compare the modern battlefield to the alien war battlefield. Surely plate armor increased survival rates back in the Renaissance, but in this day and age, it would probably *decrease* them, as any slight protection against bullets and flak it might give is more than offset by worse mobility and lack of camouflage. Same could happen here - sure, wear an Interceptor or Dragonscale (which might be actually better, since it's made of metal), but your TU's and reactions should be affected... does the extra armor offset these disadvantages?
@Solar:
Yes and no. Remember, X-COM aren't army, they start with a modest armory and have to buy everything, and pay for everything. And top-notch body armor is more expensive than rifles. Otoh if they have experimental anti-alien weapons like Autocannon, why not experimental armor as well? If you have the cash to buy it from the developer...
@Fox:
What about Dragonscale armor? It's made of metal, it doesn't burn like Kevlar ^^