This is why I have been saying for over a decade that a vast majority of lag is one-sided and screws the other person despite all the people trying to rationalize "oh lag is mutual, it's affecting both of us"...
Chances are
@nwo just usually ends up getting the shit end of the stick
You're right, lag is not always mutual and ping is only one layer of the online problems. There's different types of lag, especially on MAME because we're all on different hardware.
I need to research this more because I have a lot of theories, but there's GPU lag (if the game drops below 55fps) and CPU lag (if the emulation speed drops below 100%). We have something called "/lagstat" on Kailllera that shows which players have lagspikes, but I don't think it detects GPU lag, and it might not even detect a drop in the emulation speed. It needs to be tested, because the next Mame version might have an "advanced lag detection" feature to warn the other players if someone is lagging (and which player).
You might be thinking, who the hell can't run this game full speed in 2019? My theory is that some people who are on older PC's or even newer non-gaming PC's/Laptops might have their desktop resolution set too high and the game is dropping below 55fps (fraps shows 55fps for umk3).
That's why I asked you to voice your opinions on what aspects of the characters moved in placement specifically affect them being better or worse online, for example i mentioned Lao's teleport, another good example is not being able to block after Nightwolf's Axe-ender and the next rushdown HK-starter, Ermac losing juggle freedom, height of IA-projectiles, etc
I didn't really want to get into it because everyones online experience might vary, but in general online is slower paced, there's dropped inputs, and the speed of the game can change mid-match (which can mess up your input timing, especially on higher execution combos/infinities).
This is some of my reasoning for some of the changes (mostly top tier), I can talk about it all day, but I don't want to...
For h.Smoke and Ermac, they have a simple pop-up (LK, LP) which can set up 50%+ damage combo's, they stay the same or move up. Nightwolf's shoulder charge is fast and the input is simple (F,F,LK) and he can slip it in during his rush down and if it lands it will keep him on offense. Kitana's instant air fan is a fast and big projectile that's harder to avoid in delay, she runs in right behind it and even if you block it she gets free offense. Robot Smoke has a very quick spear, and it gets nastier in more delay. Kabal's spin is still fast and he can spam instant air fireballs even in delay. Mileena's ground roll is fast online, and even if its blocked its much harder to punish with an infinite (for Kung Lao, and probably Reptile).
As far as Lao's teleport, I think teleporting to auto combo is pretty cheap online (it works better online), but if you do it too often the opponent might see a pattern and punish it frequently. Offline it will still land, but my fighting style is completely different (there's a lot more offensive pressure when the game is running full speed) and I teleport a lot less making it less predictable. If the opponent is punishing it too often I might stop completely, but there is such things as a safe teleport (to auto combo), vs Jax double missiles, Stryker grenades, Sindel's (out of range) scream, if Kabal is spamming his fireballs, Kitana's (out of range) fan lift you can teleport and walk up behind her and spin. A lot of times you teleport just to not get cornered, like vs Kitana if she throws a fan and starts running in, you might teleport to not get cornered.