I have all 3. My rice cooker is used almost weekly and nearly solely for rice. I dont like using my instapot for rice because chances are my main dish is being cooked in it.
My slow cooker has taken a backseat lately, and only brought out for parties or large batch cooking. I have completely stopped using it for broth and stock. Nearly every time the broth would burn even on low. If I'm doing a braised meat it tends to go in my dutch oven on the stove to get the proper crispy caramelizing.
The instantpot shines for me when cooking game meat. 1 whole rabbit fits nicely in my 6qt and is pull off the bone tender in 30min. And dont get me started on how nice venison is coming out of there. Granted I do tend to do a 2 stage cooking where meat is pressure cooked and then browned/crisped under the broiler.
I also really REALLY like my instapot for small batch steam canning. I dont need to dig out my big ole water bath canner, wait for that to come to temp all while pumping steam into my house for just 5 pints of jam or sauce. It only takes maybe 40 min total for 1 batch. From pressure sterilizing my jars to pulling the jars out to cool.
Oh and broth definatley for broth. 1 roasted chicken carcass, 1 carrot 1 celery 1 small onion,1 clove garlic, 1/2 small bay leaf, salt and peppercorns, fill water to the max line and 45 min under pressure. The bones will crumble as you pull them out and no Burning!