Question about the と particle in comparative constructs

Question

I've been making my way through the book Elementary Japanese Volume 1 and in the chapter on comparatives it introduced this construction:

AとBとでは、どちらの方がXですか。Between A and B, which one is X-er?
AとBとでは、Aの方がBよりXです。 Between A and B, A is X-er than B.

If I understood it correctly then the particles で and は are acting as they normally would. Meaning the で here is the location marker and marks the range of things we are comparing. And the は particle just marks the whole first part as the topic. However, what I don't understand is the use of the と particle at the end of the list, right after B.
I think I have seen this construct without this と. So what exactly is it's function there?

Answer 1

It's also the listing-と. Originally, the standard way to say "A and B" was AとBと, using と twice. In modern Japanese, the second と is usually dropped, but it's still sometimes inserted for several reasons:

• To emphasize a comparison
• To make a sentence/title sound literary and sonorous (see the first link below for examples)
• To increase the readability of a complicated long sentence by explicitly marking what are listed (see the last link below)

In your example, the second と is purely optional, and dropping it doesn't change the meaning of the sentence. Still, I feel the second と somehow appears often in a context of choosing one from multiple options.

See also:

• 「X」と「Y」と - how does the second と affect the sentence?
• Why is there a と in front of 別?
• Meaning of と in this sentence