Nuance between でいい and でもいい

Question

Follow up question to this one :

Sentence structure and meaning

About this sentence :

「ただしお前達の相手は私一人でいい。」

It seemed to me that in Tokyo Nagoya's answer, でいい sounded a lot like でもいい :

" Meaning-wise, however, 「でいい」 adds much more [than だ]. It expresses the speaker's agreement to the fighting rules that could possibly be disadvantageous to him. In other words, the speaker is already very confident of his victory as he speaks. "

So I did a bit of research and found these :

Is 「でいい」 the same as 「でもいい」?

http://www.guidetojapanese.org/learn/grammar/must

The first link says that でもいい has a sense of "something is better out there, but you settle for less" that でいい doesn't have.

The second link says that "In casual speech, 「～てもいい」 sometimes get shortened to just 「～ていい」."

So is でいい just the familiar abbreviation of でもいい or are they 2 distinct (though similar) structures with different nuances?

Answer 1

The same as "also" in English. The word "も" implies the existence of another option.

「お前達の相手は私一人でいい。」 is natural. Simply, the speaker must be very confident about the fight against many opponents in front of him.

「お前達の相手は私一人でもいい。」 sounds weird, but it seems that the speaker implies another person stronger than him is standing by.

カレーライスでいい。 = Curry and rice is acceptable / enough / OK.

カレーライスでもいい。 = Curry and rice is also acceptable (but implies the speaker has other choices in his mind.)