I do believe I spoke with Royal Canin and they have a vet on staff who
might give you some opinions. He did not seem biased when I spoke with
him. They own Waltham and IVD.

My cat now will eat the better Fancy Feast Grilled Tuna/Chicken Feast
which is about 71-74 kilocalories per can and 0.81% phosphorus, dry
matter basis, in one sitting. Interesting. I also found that at times,
not feeding her in the morning on demand, she will actually drink a
long drink of water which aids greatly in preventing cystitis, the lack
of water in a dry diet is a main culprit.

I give some SD Oral or Light for the teeth.

It's a tough call but one European research article tied dried food to
crystals in the urine without much room for doubt. That said, I had one
vet tell me he does not see cats on Iams or SD with cystitis. I don't
know. I have seen cats thrive on cheaper dry food. But I do wonder
about the companies who seem to have more research, for example,
Science Diet will set the pH to 6.4 to 6.6 for its older cats which I
like. Try finding that on more cat food web sites where they don't even
list phosphorus content or calories. Phosphorus may be some you wish to
look into. It affects bones and can increase bone problems if I recall
correctly, which I may not. I am writing too much.

I find being mean, if I set out a decent wet food, like a better SD or
one of the few good Fancy Feast or even a very expensive organic food,
she will eat it if I refuse to give her anything else. Sometimes if I
think the food is fine, I will just let it out for hours and it's eaten
by morning. I worry about bacteria so I'm careful with the tuna types
but cat's generally have a gut that can handle bacteria. Of course, if
she's older, I don't know. But so far it's been good with canned food.
I was astonished that she will now finish a good quality Fancy Feast,
most FF have bad specs, high phosphorus which is not good, in 10
minutes now. You can read previous threads on the handful of Fancy
Feasts that have low phosphorus. The Science Diet usually has low
phosphorus so I use the Light or the Turkey and Giblets, although the
Turkey has higher calories.

I probably talked too much but that's because I am not a vet and my
knowledge is mostly limited to my immediate interaction with my
particular cat who is a bit younger than yours.

You might want to chat up some vets if that's possible. Although some
don't really get into this.

If your cat is overweight a tad, as most are, I might be a little
meaner in getting her to eat the right foods. Of course, there is
always the danger that the cat knows best and her instincts are better.
My cat refuses all beef from FF and I think she's smart, knowing Mad
Cow disease is not being discussed with cat food or pet food in general
and stricter guidelines are going into effect.

I would go with the mature indoor. They originally had a senior which
did great things for my 18 year old cat. He was walking faster, even
trotting, and taking the stairs a lot better when I switched him to the
senior food. They redid their foods and the senior was replaced by the
mature indoor and the mature active. The indoor is for less active
(older) kitties, and that is what I put my 11 year old cat on. She
isn't senior like Maynard was, but she's not overly active (except when
being chased). I do see her being more active and playful. Possibly
because of the food and maybe because of the changes in the hierarchy
(Maynard gone, and two younger ones in).

The mature indoor does have a good amount of glucosamine, more then the
previous senior (which I know helped Maynard with his arthtritis), and
I believe even more than the maine coon version.

I haven't tried the other brands you mentioned, so I can't compare
them. I can tell you that Maynard was much improved on the senior food.
He moved and felt better. Jay Jay, my part maine coon, loves the maine
coon version, and is very happy and healthy. I switched him because our
regular food was giving him the runs when I adopted him. After
switching him, he has been solid and less stinky. And his fur is softer
too. Kira, the 11 year old, liked Maynard's food, so I decided to quit
the regular food and stick with the Royal canin.

It's a bit spendier, but I am happy with the results. Advice to save
money - buy the largest bags you can get, and if possible, go to the
local cat shows and buy it from a dealer. I can get a 15 lb bag from a
dealer for the same price as two 3 lb bags in the store. I do my best
to buy the larger bags at the shows and only buy from the store if I
run out before the next show.