Given two roughly equivalent memory care facilities, would it be better to place my husband in one near me, or near my two sons?

Skipping ahead, do you see yourself living in your current area in the longer term? Or would you like to move closer to your sons? That may weigh too.

Yes, his care is more than you can handle that is why you are trying to make a decision where to place your husband.
Your two sons I imagine both have families.
Your two sons I also imagine are still working.
Your two sons both probably have homes that need their attention and upkeep on weekends.
I also imagine that when your sons have time off they want to spend that time with their families and doing things they like doing.
EVERYONE has great intentions to visit everyday or visit every week.
I am sure their intention is great but life gets in the way of good intentions.

The care that is getting to be a lot for you will be handled mostly by the staff at the Memory Care facility that you choose.
Any doctor visits away from the facility can pretty easily be provided by the facility or by medical transport if you can not manage. But you can arrange to go with him. Could your sons do the same if the appointment was on a Monday at 10:30? (or would they as their wife to take him?)
Are you going to want to drive 80 miles round trip even 1 time a week?

Now..I'm just going to toss this out...
Does the Memory Care facility also have Assisted or Independent Living in the same community?
If so would you consider moving to AL or IL in the same community?
You would be closer to your sons. you would get the help that you probably will need during your rehab with both the knee and shoulder.

How often will you want to see your husband? Unless your sons have a track record of regular visits despite the current inconvenience, moving your husband near them would be a bit of a gamble. They might set up a workable schedule between them, or it might turn out to have been what seemed like a good idea at the time and you'll find yourself too far away to go by cab and with two sons blaming one another for not doing enough. For people who are "too busy," one mile or one hundred miles isn't the important difference.

But look further ahead - would this be a good time for you to think about moving to live closer to their home town too?

I'm guessing that you will feel the need to visit more than either of your sons, so I would choose the home that makes your life easier. My mom's 1st NH was an easy 15/20 minute drive away but it was so much easier once she got a room at the one in my town, I could easily pop in whenever I was in the mood, sometimes even more than once in a day.

Looks like the sons are more than willing, and have placed the ball in your court. I would do as you think best for yourself at this point.

Has there been any discussion about your son's abilities to get you to visits with hubby in future, say several times a month? Perhaps with stopover at their homes? I can't tell what in depth family discussions you have or have not had. 40 minutes isn't that bad. It took me an hour to travel to work and home by bus when I worked.
It just depends on how you look at it and what is best for YOU, I think.

I feel near you would be better, as it would be easier for them to drive and one of them can come on different days.
And you can still go less if in fact that is feasible.
Only you can answer that as you know your children.

Near the sons. Those that need help owe it to those helping to make it as easy on them as possible!

Also consider moving yourself. Make it your decision instead of this becoming something your sons have to decide for you. You’ve read enough of our horror stories on here to know how torturous it is to have to move a parent when they’re being difficult and don’t want to move even though every day living alone is precarious. 1 in 6 over 80 have some sort of dementia. Plan for your own future.

You could actually enjoy an assisted living! 3 meals cooked plus laundry and cleaning and somebody else planning activities? Not to mention people in your situation to befriend. My mom is in assisted living and dad is in memory care. My mom is a pill and refuses to participate in life, however. (This isn’t new behavior, it’s who she is as a person.) When I visit I see other ladies choosing to enjoy it. My mom will go get my dad from MC and bring him up to the spa with her for hair and nails and a shave … because lord knows if you choose to lock yourself in an apartment all day taking room service your hair needs to be freshly colored at all times.

near sons, with their likley busy lives 40 (x2) min away is a whole arrangement but near them they can go at convenience , also more of them to share the load especially if dils and grands can also , discuss expectations beforehand as far as minimum expected visits and interaction with staff— if they are willing can take this staff liaison thing over for you , also the grands are more likley to visit when closer so they don’t miss out on their other activities, if feasible you might also be able to recouperate there - if that facility has rehab possibly even a short stay there and or at son’s home if okay with all- you need to think about yourself as well and you may not be able to drive even short distances while recovering from surgeries. Also consider your own long term plans — are you in own home now , would you be happy in an assisted or independent living situation , ? Best of luck

Place him near your sons. It will be much harder for your sons, who probably have busy lives of their own, to travel to you and their father than for you to travel to see your sons and your husband. Make it easier on your sons to help you.

Between two equally wonderful continuing care facilities, my son, daughter-in-law, and I decided on the facility closest to our son and his family. Our son and his family are professionals with extremely busy lives. I am retired and have more time to travel. Placing my husband so close to our son and family was so convenient for them that they surprise hubby with his favorite treats on their way home from work and school. Their visits provide happy vibes to my husband's dementia world. Because of my husband's convenient location for our son, I took a hint and sold our home to move a couple of miles from my hubby's facility and our son's home. It has been five months since I moved and I am feeling quite smug with the brilliance of my decision. Living this close to our son and my husband is healthy for me and my husband, both physically and emotionally.