Thanks, jrueter. You're correct, the mirrors will be frameless, whether beveled or not..

definitely- beveled will look best!!

Beveled will look more finished.

I had to think about this one before I answered for a while.

Because they are oval I am going to say "plain", and here is why:

I carried home a super cheap oval mirror from Home Depot because I knew I was selling and did not want to spend a lot of money on it. It's mass produced and has a wide bevel.

In our temporary rental the bathroom was updated with a cheap medicine cabinet and light fixture again from Home Depot. The mirror is oval, and it has a wide bevel. It's not that old and it's peeling.

So my direct experience and some other looking at real estate has been with a lot of oval mirrors that are beveled but obviously cheap.

If I was spending for custom mirrors I would not want them to look like I just got them at Home Depot.

So I vote plain.

I think an unbeveled would look more modern. I am thinking beveled would be too traditional.

I think like enduring that the beveled is more traditional . My opinion is that the oval shape by itself is more traditional , so adding to it the bevel will make it too traditional for this modern bathroom . If you didn't have the led light I would have suggested to you to frame them the same color as the vanity.
Your bathroom is progressing nicely , I like the slate on the wall a lot . Good luck with the paint color . I will leave it to the experts on the decorating forum to help you finding the right color.

Your bathroom is coming along wonderfully. I assume the mirrors are frameless. I just like your idea, i had Rak Mirror in my bathroom. this Rak Mirrors Range Infinity LED mirror in a stylish design on/off rocker switch

Thanks, everyone, for all of your help. Since it was a "split decision" I decided to get out to the glass company to actually see their mirrors in person. They had a 36" x 24" beveled oval and it was gorgeous. Nearby was an unbeveled rectangular mirror and it looked, frankly, somewhat cheap. To be fair, it's possible that the oval shape might give a different impression but I decided not to take the chance and ordered our mirrors with a 1" bevel.

Palimpsest, your experience got me thinking about an oval mirror I bought at Home Goods when I was testing out sizes. It's smaller than the ones that we ordered and has a beveled edge. I dug it out to take a look at it just now. It looks really cheap also. Why? Well, I measured it as only 1/8" thick and the ones in the glass showroom are 1/4" thick which affords a nice deep bevel. I think that makes a big difference.

So, thanks again for the help!