I auditioned the Cornwall IV's and loved them. But I didn't think the imaging was quite as good as what I wanted, so I went with the Ardens, without auditioning them, on a lark.
I think they would be perfect for your size room. Both are relatively unsightly compared to other options (according to some. I loved both)... But the sound...
If you get a chance to audition them broken in, that would be wise. The Tannoys do take about 500 hours to losen up. And it's not a pretty journey at times.
I can say the Cornwalls are likely better for low-level listening. They are incredible speakers and just effortless.
But if you can open them up... The Tannoys have left me with no regrets what-so-ever. They make almost everything sound realistic. They are a blast. They are alive. They are what I remember liking the best about live music. But they can put it out. While I was breaking them in, I put on a Boccherini cello concerto while I mowed the lawn. My neighbor stopped by and said: "Those speakers sound great! Where are they?" and I had to tell him with a straight face: "In the house."
Both have to be a pulled a good ways into the room to get a good stereo image. Same as most speakers. Soundstage is just more complete with the Tannoys, IMHO. But it all depends on what you are looking for. I honestly don't think you can go too far wrong with either.
Best!
Steve