Depends on the era and type of device. Original Playstation CD's are really crappy and are easily scratched within the console after long playing, so emulation. PS2 and GC are much better, but they are pretty bad too (Don't think some games liked being played for 100s hours). PS3 thankfully fixes this issue, even if you could emulate that damn thing.  

I prefer original hardware

For cartridge based consoles I prefer the original hardware, although in some cases with expensive games I may consider playing with a VC copy instead. I tend to avoid playing with PS1/Dreamcast discs though, if there is an alternative on PSN/Steam I'll go with that instead.

Nothing feels better than playing the original... ; ) Unless the game is impossible to get, I go for the physical option.

I still have my original SNES (though a lot of the games are missing) and I wouldn't go back. I was always "anti-emulation" for some noble reason but once I learned how to emulate, I never looked back. I can restart that frustrating area, I can improve the frame rate on Star Fox, etc. Yeah, the original hardware has that old school charm and nostalgia factor but I'm gonna have to go with emulation.

Original Hardware. You can't emulate the 'true' experience.

Virtual Console. I mean, it's basically legal emulation and the games work at least 99% the same as the original consoles. Plus, you can remap the buttons and use save states, which are really useful features.

Nothing beats playing games on the original hardware. On top of that play games on emulators just isn't as satisfying I don't get the same joy from downloading a random rom that I get from actually tracking down an original copy of something then playing it on my CRT

Original hardware
Its more relliable and stable experience and its easier to use. The controllers are also authentic. And i have a huge physical backlog which i havent even finished yet, so i have no excuse for downloading every rom i want.

I only use the PS3 emulator for my disc based PS1 games because it actually is working like its supposed to be in 90% of the games. And i have a PS3 Memorycard adapter where i can switch files from PS1, PS2 and PS3 back and fort.

Emulation..  Having 10 consoles in my living room is not my type of thing..