[cladopa]

It deeds on the game and technology that you try to emulate. I wrote home-brew emulator software for the Nintendo DS. I could play Sega Genesis games without problems but some SNintendo games like StarFox game me literally headaches. Why? Because the SNES included special chips in the cartridge that were painful to emulate, badly documented and gave you screen flickering and stuff.

Those consoles are so old now that you could emulate them with anything, a Chinese chip that cost dollars will do. But you will be extremely wasteful, consuming tens or hundreds of times more energy(less battery time) for a worse result.

Software is way more flexible. Everything is prototyped first in software. In the past there were machines that consumed a hundredth of a watt of energy. Emulating them using 20Watts is so wasteful.

With software you had only one thing that needs to do totally different things. With hardware you can choreograph a chip working in parallel among others in an independent way.