I think there is more of a difference between drivers on Linux. Maybe speed difference also people with different CPUs? Some have posted their personal optimizations, but it is hard to judge typical speeds for sure.
CZM 1.1 gave me similar speeds for Windows and Linux on the same machine with RX470 x 2, 1GB or RAM and very old and slow CPU. Other Linux miner was not able to give the same due to high CPU requirements. Now the same machine runs 4.0 under Windows. So, at least one problem with "other miner" is high CPU usage.
I don't like to use Linux because in general it is a royal pain to set things up. I would use it to get 6 cards on ASrock H81 BTC PRO boards, but when I set up, was dual mining, and can't undervolt in Linux. Some cards I can bios mod, so I could do it now, I just don't want to mess with it, and Win7 can do 5 cards with some MB Bios changes. I have used it before from time to time, and tried getting it going on HTPC, but ran into too many issues. Also When Ubuntu changed to new garbage UI, turned me off more. I know you can switch window managers, or use diff distro, but that's also more work. If I wasn't as busy, and have 5 kids, I would consider it more. I use Ubuntu Server VMs for work some though (web/android dev). So not against it, I just use what works best for me.
I would tell the same Re: Windows. For headless rigs it is a pain in the ass. I used to run ubuntu off 1GB USB flash and never had any problem. Neither had GUI. Now I have to use 16GB USB flash and run Windows 10 To Go from them. I miss ssh for configuration.
It's not about money, there are several reasons why I'm not going to release ZCash miner for Linux in near future - most of haters who say that I stole SA engine are on Linux so let's they use some different miner. Also I don't like to see as someone applies IDA to my miner to see how it works.
All those may switch to Windows and continue running your miner. Also for those who concerned, it is not too difficult to run IDA on decrypted Windows code. It's just a matter of skills and efforts. Formally say, they studied your code the same way as you might study theirs (open source), and I didn't remember where your readme files explicitly prohibited reverse engineering. Still, I understand you (because somehow I am similar to you in that regard). But a lot of users miss Linux version, still being able to run Windows if no other comparable option exists yet.