Difference between が and でも in this sentence

Question

What's the difference in meaning between these sentences?

どちらか片方が罪を背負った方が良い。

and

どちらか片方でも罪を背負った方が良い。

I thought their meaning was the same, but I get the feeling it's not because of the particles.

Answer 1

These two have a major difference in meanings.

どちらか片方が罪を背負った方が良い。

Either of two should bear the sin.

どちらか片方でも罪を背負った方が良い。

At least one of the two should bear the sin.

The latter sentence is very close to the sentence below:

どちらか片方だけでも罪を背負ったほうが良い。

And the following dictionary entry (quoted from デジタル大辞林) the best applies to でも in the latter sentence:

［係助］《断定の助動詞「だ」の連用形＋係助詞「も」から》名詞または名詞に準じる語、助詞に付く。

物事の一部分を挙げて、他の場合はまして、ということを類推させる意を表す。…でさえ。「子供―できる」「昼前―気温が三〇度ある」

So it implies that the best choice is both bear the sin, but only one person is still better than no one bears.

Regarding the former sentence, both is not allowed as its subject is clearly 片方.