ok so I played Final Fantasy 1 and 4 back to back and thought they were both amazing. Any reason to get the Steam version over the Virtual console versions?
Specifically for which game are you talking about?
Final Fantasy 1 isnt on Steam - at least not yet.
Final Fantasy 4 on Steam is the 3D remake which originally was released on Nintendo DS and re-released on mobile. The Steam version consists of additional features that were added to the iOS/android version which were improvements from the Nintendo DS verion including the option to change difficulty, enhanced visual graphics, and 58 achievements. The 3D remake also introduces a remixed OST and a lot of new gameplay elements that were not on the SNES, PSX, PSP or GBA version but unfortunately does not consists of any of the post game dungeons from the PSP or GBA versions.
The sequel to Final Fantasy 4 - which is "Final Fantasy IV The After Years" is a 3D remake similar to the Final Fantasy IV 3D remake - compared to the Wii and PSP versions which were 2D.
As for Final Fantasy 6 itself - the Steam version is a port of the iOS/android version which introduces a new visual design compared to previous games but also includes the GBA version's post game dungeon which the SNES and PSX versions lacked. Also includes achievements as well.