I want my arena visible to someone. I don’t care if it’s a public road or my house, but the idea of falling off of a horse and having no one who would be able to see me is a bit scary. So personally, I would prefer to have the arena close to the house even if it means that you’ll be introducing dust fairly close. This seems like a morbid thought, but the idea that I could perhaps crawl toward my house if I needed to is something I would be thinking about since I’m often riding alone on the property. And it was definitely on my mind when I had a horse fall on me while jumping a couple of years ago resulting in a bunch of broken ribs. Boy was I glad that my arena was close to my barn which is close to my house. But having the arena that close does have the con that it will get dusty. Fortunately, that’s only an issue a couple of months a year around here.
I do think that sacrificing a little length for width is not a bad plan. I would greatly prefer a 76’ width to a 66’ width. I think you get more bang for your buck with the greater width, while length is a relatively moot point if you’re not going to be jumping really big fences.