As mentioned in a previous answer, Windows IoT is not real time operating system. But what does that REALLY mean?
You only require a RISC OS like Arduino or PIC if:
- You need to repeat specific actions in extremely accurate intervals. For example software oscillator, reading sensor values in exact (atomic) intercals or software bit banging (UART/SPI)
You need to measure interrupts from other devices in extremely precise times. Like a laser finish line with accuracy within micro seconds (<1ms)
An event driven operating system like Raspbian or Windows IoT is perfectly suited for your application because:
The Raspberry Pi hardware handles inputs by using hardware interrupts and raising an event in the OS.
So what does that mean? Unless you need exactly precise (micro seconds!?), or atomic timing you can use any kind of Event Driven OS, like Windows IoT or Raspbian.
It means that the Pi actually measures the button click within several CPU cycles (thats faaaaast) and the OS will process it as soon as it can.
So unless your CPU/GPU is 100% overloaded with video encoding or something then you will not experience any thing more than 20~100ms added time after clicking a button. (Where 100ms is pretty excessive over estimation on even a 50% CPU usage) It doesn't take much to process an event in these OS's - It just is not micro second precise.
The same phenomena applies to all Personal Computers. I am sure you have played
RPG game. The difference between you making a head shot or your
opponent, is who can compensate better for the delay between human <> OS
<> network lag.