Looking at the datasheet for the lm311, the output is a transistor (I think it’s shown on your schematic), the reason you need a pull-up on it is because it has no bias or power. That will let it pull the voltage down. If you’re noting that it doesn’t rise fast enough, try making that 100k smaller, give it some more strength.

. The 741 on the other hand has a pair of transistors on the output stage, attached to +v and -v so it can push and pull the output