There's really nothing wrong with the original version of Chrono Trigger, and it's the version I would recommend picking up if you can wait for it. Now, Chrono Trigger had minor translation issues that got tightened up in later retranslations, but they were so minor that it doesn't matter all that much IMO. And hey, you can enjoy Crono passing out from "eating too much soup" instead of "getting totally smashed on Sake".
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Looking at the DS port of Chrono Trigger, honestly the things they added didn't really improve the game much. You have 2 new dungeons (including one cut from the original game), but neither of them are altogether well-done and one of them is a pure chore to work through due to constant backtracking. There's a new ending as well that tries again
to make Chrono Cross relevant, but it's nothing special really. There's a new monster arena mini-game added for the DS version, but it sucks so it's not worth bothering with. The DS version also adds the anime FMVs from the Playstation version, which are kind of neat but the problem is that they play alongside their original SNES cutscenes (so you see the same scenes twice in a row). Finally, I don't know why (and you would only even notice or care that this was changed if you were a huge Chrono Trigger fan) but there was this one audio effect removed from the game for the Playstation and DS versions of the game. It was this little "WOOSH!" sound and visual effect that would always play when you had a screen wipe during a dramatic moment (such as in the attract mode demo and the Rainbow Shell quest), and it was replaced with no sound effect and just the screen fading out. Little things like that bug me about the DS version.
So yeah, wait for the VC version for CT. It's cheaper, you can play it on a big TV with a Classic Controller (Pro), and I pretty much prefer the original versions of that game. As for FF IV, I would probably recommend the GBA version if you can find it, or get the PSP collection that just released. The original version of FF IV just has major localization issues, some from Nintendo's inane censorship policies at the time and some from the then-Japan view on America not being able to handle difficult games.