Real hardware is nice when it's an option, but for a lot of retro games the price is going to be a massive roadblock, so in many cases emulation is just the more reasonable choice.

Real hardware if you can, but emulation works perfectly fine imo.

Real hardware if I can, but emulation nowadays is amazing, especially Dolphin.

For me, playing on real hardware has a certain charm and emotional appeal, similar to how reading a real book feels more authentic than reading on a Kindle or tablet.

Just as I prefer to own my games physically, I enjoy collecting, looking at, and using retro hardware, I find them fascinating as glimpses into a certain time in gaming history.

Emulation, just the sheer fact that it's much better for me financially than going out and buying every old console and then the physical game (especially some games, as they've become very expensive)

Edit: But if money were no issue, then real hardware would win all the way. 

I haven't downloaded an NES emulator yet (I will) but I have the virtual console on Switch and I didn't remember Mario Bros. gravity being so heavy? I'm assuming there was one version of the game although I could be wrong but it isn't very appealing. I also remember buying a Gameboy version about 15 years ago that felt heavy too. I'll respond once I get my hands on an emulated version for android.

Real hardware as much as I can. Game was made for that hardware with that controller in mind. So it's a full experience. Even something as simple as Sonic. One thing to play Sonic 2 on an Xbox controller but it feels better playing on a Genesis controller since it was made for it. I get it. Old consoles are dying. Take up space. Expensive. So I don't have anything against EMU for old games. I am getting a Polymega myself and I did get a TG16 Mini so even I am beginning to see my options as these older consoles become less of an option. Suddenly my Dreamcast went from 4 years old to 21 years old without me noticing until it was late. Still works but for how much longer? So hopefully there is a good DC emu machine out soon to play DC discs.

Real hardware, because I already own it all, and love collecting.