Balloon and Giant Skeleton both the troops are found in Bone Pit(Arena 2). Both of them are epic. So it is not so easy to unlock those. Now there are some advantages as well as some disadvantages of using those. Balloon has a high damage(1158 in max lvl) and low death damage(193 in max lvl). But the problem is that its hitpoints is very low(2026 in max lvl). A Minipn Horde or a Musketeer can take it easily. And Giant Skeleton causes low damage(193 in max lvl) and high death damage(1389 in max lvl). But its hitpoints is high enough(3860 in max lvl).So giant Skeleton is opposite to Ballooon. But both of them are very useful one for offense and another for defense. Normally arage and arrow should be used with balloon and also freeze. And Giant Skeleton should also be used with arrow.