I'm a latecomer to running game online, but here are my anecdotal experiences about game prep between the two.
- I have to prep minis - paint them and make sure they're in the minis trays.
- I have to prep all of my paper books and notes to bring with me to game
- I have to pack lunch and snacks
- I have to scour lots of images to find "minis" or send pictures of the ones I want to one of my gamers to edit into icons.
- prepare battle maps to save time in session
- prepare dungeon maps & deal with FOW
- assign out dynamic lighting, etc. for characters.
- I have to restock and review the dungeon areas I expect the PCs to travel to.
- write rumors
- deal with last-minute questions about spellstones, scrolls, skills, and point-spending.
It's a change - I have all of these minis, and encounters prepared around specific ones. I have battles that aren't in setpiece locations, so I can't just pre-prep them. It's taking soem getting used to . . . I can't fly by the seat of my pants as much online without having things grind to a halt. It's a learning curve.