Regardless of whether an army is all volunteer or whether it introduces compulsory service; invariably, the burdens of service in the army, especially during war time, will fall on the less privileged and unwanted members of society. That being said, the all volunteer army is more professional, more efficient and more members of the all volunteer army want to be there. I have seen where some members received some serious wounds, get prosthetic limbs and then return to combat on prosthetic limbs after proving they could pass physical fitness tests even though they didn't have to.
The dark side to the all volunteer army is that the burdens of national defense are shouldered by a very tiny fraction of the population and depending on how serious the threat of the enemy is, the civilian population won't have any "skin in the game" or face any hardship or real sacrifice that a tiny fraction of the population who are in the all volunteer force are taking on, on behalf of the nation. The plus side to compulsory service is that more members (though they will invariably be the less privileged members of society too) of the civilian population will share in the burden of national defense and a tiny fraction of the population won't have to shoulder as great of a burden (We have had one guy literally go on 15 combat tours starting in 2001 before he was killed in action on his last tour and I don't believe that is healthy for somebody to go on that many combat tours in a lifetime much less in that period of time).
Civilian populations who are exposed to compulsory service, I think, are more apt to put the best interests of the country first in some cases than their own selfish interests and are also more apt to compromise with opposing political parties given that they were required to give something and sacrifice something for something that is much more larger than themselves. They thus have more "skin in the game" and will thus have more "skin in the game" in assuring the best interests of the country as civilians rather than solely and strictly their own selfish interests. You see that a lot with the World War II generation who faced conscription on a mass scale to fight mankind's most bloodiest and most devastating war in history.
"All in all the time." -US Navy SEAL saying
"Put everything you’ve got in what you do. If you do that, win or lose, you will be a champion." -PO