For me, it depends a lot on what I'm planning to use the machine for.

For web development, I prefer Mac or Linux because I like to be able to do everything on one machine and usually prefer CLI tools. I personally feel like switching to a VM for development would get annoying pretty quickly, but lots of people are okay with that.

You mentioned that you've tried Linux and that the UI was too sluggish. There are lots of distributions out there, so if you limited yourself to just one, it might be worth it to check out some other ones. If you do, keep in mind that some software (Photoshop, etc.) won't run on it. You could use VM (or possibly Wine) to use that stuff, but you'd want to take into account how often you use them. You'd still run into the problem of switching to a VM for certain things with that though. My own experiences:

- Ubuntu was slow for me when I originally tried it; I think they had just started using Unity at the time, and it was terribly buggy and slow for me. I didn't like the design of the interface much either, so I haven't really tried it since then. This is probably the most popular distribution out there, so if it's the one you tried, it might be worth playing with the other ones in a VM to see what you think.

- Linux Mint is fairly popular and a derivative of Ubuntu. Cinnamon and MATE are the default desktop environments for Mint, and most people really seem to enjoy them. During the brief time I played with it, I liked it.

- Debian is a rock-solid distro. It's stable, pretty minimal, and has always run well for me. The packages will probably be outdated because they stick with older releases with better stability, but you can repositories with more up-to-date packages. I used GNOME Shell on it and it was very smooth.

- Fedora is more bleeding edge than Debian is in the Red Hat camp. It's a popular one and uses GNOME Shell by default. It's not as stable, though I never ran into any stability problems myself.

- Elementary OS is pretty nice and based on Ubuntu. It looks a bit like OS X, so you might appreciate the familiarity. I tried it on an older laptop and it was slow, but the hardware is old enough that it won't even run Minecraft, so your experience would almost certainly be better than mine.

- Arch is very minimal (you install everything yourself), so it is very light on resources if you don't bloat it up, but it will probably take a good chunk of time to get set up. It's my preference, but for something that "just works," I wouldn't recommend it.

One of my buddies has had pretty good luck with Bash on Windows. He doesn't do any web development with it, so I can't really vouch for it, but it might still be worth looking into. Another friend says it has worked really well for him too, but I don't know if he's used Ruby with it or not. I will probably wait until it gets pushed to the regular release to use it. There are a lot more tools on Windows for other areas of interest to me, and lack of a good option for CLI tools has kept me from switching back, but Bash on Windows might be enough to make it a viable option again.

That might not have really helped much, but I thought I'd still offer my two cents. What tools do/did you use on your Mac?