I would advise basing your decision on what the car has now, and completely ignore any promises Elon makes on investor day.
Do you depend on parking warnings where you usually park? If so the Ioniq might be better. If you prefer a softer suspension then the Ioniq might be better.
I don't know what kind of driver assist the Ioniq has, but in general the AP/FSD is pretty good and it keeps improving. I use TACC regularly, on the freeway in heavy traffic. I really love driving the car and I have no interest in "letting the robot drive." It's my first electric car and I love the smooth acceleration. The car is a blast to drive.
Do you know anyone else in your area with a Tesla? Ask them if they use any of the AP/FSD features - and if they experience phantom braking. My neighbor and I know about a few locations where the car mysteriously slows, every time. There are known locations. Also, the FSD is an extremely careful driver - it doesn't drive like a human, and I usually don't have the patience.
I have a 2023 without the USS and while I've gotten used to it, I bought my MYLR believing the "features are coming soon." I've decided for my own peace of mind that my car will never have parking warnings. I haven't seen anything from HW4 rumors that it will restore these features. Also we don't know when HW4 will be out, regardless of what Elon says.