For pressure cooked meat, I find if you do slow release (so just let it sit for 20 minutes or so) rather than de-pressurizing quickly, that makes the meat actually more tender and juicy than slow-cooked meat. Back before the Instant Pot, I actually had three slow-cookers in varying sizes that I used all the time, so I do have quite a bit of experience with slow-cooked food and I do believe pressurized food is superior in quality. I gave away all my slow-cookers after we got an Instant Pot and I never miss them. We do also have a cheap rice-cooker that I will never get rid of, but we only use it for rice.
As far as the slow-cooker function, we almost never use it anymore because we like pressurized food so much more. Also, I have found it to be true that the slow-cooker function on the Instant Pot doesn't work as well as a dedicated slow-cooker. However, one work-around for the slow-cooker fucntion is to cook everything on sautee first (because it gets things hot much quicker) and then change to the slow cooker setting. Another is to sautee and then put it on the keep-warm function. Sautee turns off automatically after 30 minutes, so you can't use the low sautee setting as a slow-cooker.
Finally, I will echo another poster that cleaning up an Instant Pot is much easier than a slow-cooker, because you can put the stainless steel in the dishwasher. If you don't have a dishwasher, that wouldn't matter as much, but it IS much lighter and easier to clean than the heavy ceramic slow-cooker insert.