Continuing through Final Fantasy IV, I went through the Magnetic Cave and beat down the Dark Elf earlier. I was a bit surprised to find the difficulty of the dungeon completely reversed—well, kind of. In FFIV Advance, simply getting through the cave was harder than actually beating the Dark Elf; in the original FFIV, it was the opposite. It seemed like there were fewer random battles in FFIV compared to FFIVA, and the ones I did run into didn't seem nearly as bad. In particular, there were many more Cave Nagas for Tellah to suck MP out of with Osmose and many less Ogres to put the beat down on me.
The Dark Elf was a different story. I've been noticing a trend of enemies being a little faster in FFIV compared to FFIVA but the battle with the Dark Elf was the first one which was noticeably harder because of it. Specifically, it made it harder for Tellah to keep the party healed once the Dark Elf transformed into the Dark Dragon and began using its Dark Breath attack (noticing a theme here?), which hits the entire party for quite a bit of damage. Instead of getting hit by one physical attack or one Dark Breath for every turn Tellah got, I was getting hit by both every turn. That hurt a lot but the Dark Dragon goes down pretty fast so I was able to pull through without too much extra trouble.
But here comes that, "well, kind of." See, in the easy type version there's a little trick for killing the Dark Dragon: You have Tellah cast Tornado (or Weak as it's called in the easy type version), which then lets you kill it in one attack. Most bosses are immune to Tornado, for good reason, but it works on this one. But I've never gotten it to work in FFIVA so I figured that it just doesn't work in the hard type version. Except that it does in the original hard type version. So, if you know this, the fight actually becomes easier than in FFIVA.
The fight with the Dark Elf made me see how Zeromus could be harder in the original version, though. Zeromus also has a very strong, full-party attack (Big Bang—it makes Sephiroth's Super Nova seem like a joke) and if he's able to use it more often then that would raise the difficulty. However, in my FFIVA video of Zeromus I didn't even need Rosa to cast Curaja every turn so there was a fair bit of leeway there. I'm really looking forward to fighting Zeromus in the original version now.