I don't really play old games, but if I do I use the original hardware. Of course, Spyro reignited was worth it on PS4, rather than busting out my PS2+PS1 discs.

Real or official rereleases. I like my physical media.

The only time I use emulation, is if a game only exists there. An example of this is Radical Dreamers (Chrono Trigger/Cross side story), which was never released outside of Japan and never even saw an official physical format.

I prefer emulation when there are clear performance and visual benefits in doing so.

However, I also like the real hardware as it's the collector coming out in me...

So my answer is... Both?

Since I mostly play PC games, I don't really have to choose most of the time since even old DOS titles usually work perfectly fine with simple DOS-box (which is close to an emulator in many ways as well). For console games, I prefer emulators, some even allow for extra effects and better resolutions. But I've also enjoyed some of the retro machines on the market, my main gripe with these are some stupid technical solutions and a very limited library of games.

Whatever's the easiest choice. I have a PS3 installed currently, so I can use that to play PS3 and PS1 games. If I need other retro games are easiest to play using emulators at the moment, although I haven't had any time to play retro games in a long time. If I had though, I'd get an emulator.

At this time I would say emulation. There are great software out there like RetroArch, which give you the possibility to dump and play legally your own original CDs for just any retro platforms (Sega CD, PC-Engine CD, Playstation 1 & 2, Sega Saturn, Dreamcast, Gamecube, PSP) with state-of-the-art emulation on PCs, Android devices and many other platforms. With a unified interface, latest gamepads support, per game box-arts, online/local multiplayer enabled and several graphical enhancement options it's a great way to play old games and build the all-in-one retro machine of your dream. Sure, you can play any roms there, but better to stay in the legality realm and support our beloved industry whenever it's possible! ;)

Also the PolyMega seems to be quite promising.

Emulation, although for PC games on PC HW, BC goes back many generations without actually needing emulators, in this case we get the best of both solutions, and often mods, both official and user made, that allow to play old successful games with improved graphics. And when things don't go smooth immediately, both GOG and Steam do a damn good job at making updated installers.

Emulation can improve the gaming experience above what the actual hardware could do. Emulation all the way.

I like feeling the real plastic. Emulation makes me less likely to actually play the games. I for example had a ton of Virtual Console titles on my Wii U, but I didn't even touch 3/4 of them as I can recall. Conversely, I got a PS1 recently and I've played already all the games that came with it.

Emulations, Re-Releases, or Remasters, all day, every day.

Space is at a premium, both for actual physical space, and the video ports available throughout the house. When you have PlayStation, Xbox, Nintendo, AppleTV, and PC's connected, it does not leave room for any retro hardware. On top of that the shear amount of shelf space needed for Physical copies of 1,000's if not 10,000 or more games is just not feasible, at least in my situation.

In addition, the emulations typically play better, and the re-releases/remasters offer modern additions like Trophies/Achievements, Custom Music, Network Support, etc., along with much high resolutions, reworked textures, higher frame rates, and more.

Personally, I have nostalgia for the software, not the outdated hardware I was playing it on.