Dedicated AC line - Contractor wants to use BX instead of romex


I’m having a dedicated in wall AC cable run, about 40-50 ft. I was planning on using VH audio cryo’d 10-2 Romex but the contractor wants to use BX since it’s an urban area and more impervious to mice, etc.

Any thoughts on this?

Also I was planning on wiring the end of the run with an 20 Amp IEC connector so I could plug it directly into my Niagara 7000. I don’t know if they will wire it this way but I thought I could always do that myself later.
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@todd1010

I see a lot of references to using 10/2 but for some reason I used 10/3 wire.
What the differences?
Did I chose wrong?

No. You just bought one extra strand of wire that you don't need. That wire can be tied off and not used. Unless you need a 240 outlet there sometime instead? @jea48  and @Schmitty would have better understanding of that issue. I'm a Gen Contractor/ carpenter and not as qualified as they are on that issue