Question about the と particle in comparative constructs


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?




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?](https://japanese.stackexchange.com/q/30969/5010)
  * [Why is there a と in front of 別?](https://japanese.stackexchange.com/q/32765/5010)
  * [Meaning of と in this sentence](https://japanese.stackexchange.com/q/71947/5010)




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?](https://japanese.stackexchange.com/q/30969/5010)
  * [Why is there a と in front of 別?](https://japanese.stackexchange.com/q/32765/5010)
  * [Meaning of と in this sentence](https://japanese.stackexchange.com/q/71947/5010)

