I would use the larger. The length looks fine on the smaller but the diagram doesn't show the sink cut-out for width and it looks smaller than 12". You might end up with a dinky bar sink. You're also not gaining much counter space by going smaller so I don't see any advantage to it.

You can cut grocery bags to size and lay them on a counter to see how they feel.

Good idea, thank you!
I would prefer 1 sink, but if sell down the road it’s probably best to stick with 2

Also, how do you use them? Smaller might be fine for toothbrushing, but larger required for hair washing or hand laundry. You can visit sinks in a bath showroom to see how they look/feel in person.

I would prefer 1 sink, but if sell down the road it’s probably best to stick with 2

I wouldn't. I have 60" vanities, all with a single sink. If you put two sinks in a 5' vanity, you will end up with very little counter top.

I'm changing my double sink 60" vanity to a single sink but we have another bathroom on that floor.

Use is mostly tooth brushing/face washing.

We will have 2 other full bathrooms on the upper floor..I worry I will clutter up the counter if I have more space with 1 sink.

Also, it’s already roughed in for 2 sinks at this point. Not sure how that works//if you can just do 1?

I have never had the need for 2 sinks in a bathroom in 50+ years of marriage I much prefer counter space to 2 sinks .

We definitely don’t *need* 2 sinks. I don’t know how easy it would be to change the plumbing to one, though.

(Counters / cabinets have not been ordered yet. Only the plumbing rough-in is finished at the moment)

My folks installed a too small sink in one bath by accident; specs and ordered without seeing it first... (single sink, 48” or so vanity). Even with a large deck (yes it’s a wierd sink) it’s a mess. Water (toothpaste, soap drips, etc.) splashing all over. Unless it’s a powder room and only hand washing, my suggestion is larger sink is better.

What faucet brand/style is that?

Curious what size sink you used?

I'd go with the smaller sinks so you have a little more room between the basins. If you both get ready in the morning at the same time, having more clearance so you're not knocking elbows is a good idea.