This is a really hard question to answer to give a proper answer to.

Lets look at some examples.

The Soviet Union had a largely conscripted military that basically took a "keep throwing meat in the grinder until it seizes up" strategy. The army was quite ineffective and had poor moral. Though you could argue that their ineffectiveness was was due to Stalin's officer core purges, poor training and lack of equipment in comparison to the Germans and not necessarily their will to fight.

On the other side of things the United States also had a largely conscripted force but their troops were able to go almost toe to toe with the enemy. True the United States armed forces were better supplied but you would really have to look into why their conscripted troops showed a greater willingness to fight than that of their allies. This would perhaps be more of a psychological question.

Conscripted troops i would argue have the potential to be equally effective troops as those who volunteer assuming they both believe in the cause but i think generally speaking the reason why conscription is frowned upon, apart from the fact your forcing someone to do something against their will, is that when a nation is at the point where it needs to conscripted the troops are often being rushed out with proper training. I'd argue that the lack of training and opportunity to participate in drills is what calls their effectiveness into question.

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