You can make a decision based on your bathroom cabinets.If you can send photos of your bathroom, a professional can give you better advice.

If you like one large mirror, then do it. Don’t worry whether it’s dated or not. I much prefer one large mirror. And, yes, please post some pix. You’ll get more input.

It's dated even though it makes for a much better functioning bathroom.

I believe that it is so practical and inoffensive that it won't really be noticed as dated except perhaps in internet photos where the experience is very different from being there in person. I much prefer a full mirror (if I'm not doing a pre-1950s period bathroom, and a period bathroom isn't going to have two sinks anyway).

Not dated, but depends on the overall design. You want to get the scale right and decide if you want lights installed through the mirror. Holes have to be installed at the shop during production and can't be done on site.