[рони]

Winni,

function fn(c, b) {
    for (var d = [], e = {}, a = 0; a < c.length; a++) e[c[a].id] = !0;
    for (a = 0; a < b.length; a++) !e[b[a].id] && d.push(b[a]);
    return d
};
var old = [{"name":"Иван","id":"1234_SEPT_2014","country":"Москва"}, {"name":"Василий","id":"634_DES_2014","country":"Сочи"}],
current = [{"name":"Иван","id":"1234_SEPT_2014","country":"Москва"}, {"name":"Дмитрий","id":"4757_DES_2015","country":"Питер"}, {"name":"Василий","id":"634_DES_2014","country":"Сочи"}];
 alert(JSON.stringify(fn(old, current)));