In the 10+ times I've been through St Lou, half of the time I end up in the wrong lane that becomes an exit without any warning forcing me to take another scenic detour of downtown. Happened again this summer on the way out West as my GPS did not know about the new bypass coming in from the SE (I-255) and naturally I was in the wrong lane to take it and ended up going into town where I ended up in an exit lane and seeing downtown AGAIN. Unlike some I will not slow way down or force my way into a lane change at the last moment.
OP, I would take I-65 as it's newer, has longer sight distance, and has the exits marked better than I-70.