Sub microsecond jitter accuracy - what to use?
It's not clear what exactly the signals are you need to generate, and their timing relative to incoming signals.

However, 250 ns isn't really all that hard to achieve with something like a EP series dsPIC, for example.  At 70 MHz instruction rate, that gives you up to 17 instruction cycles of allowable jitter.  That's a lot.

Having your incoming signal cause a interrupt, then generating the output signals from fixed instruction timing will give you much less than 17 cycles of jitter.  It would be even better if the input signal can trigger a PWM generator or the like.  But, you haven't given enough information about the nature of the output signals to know whether specific hardware available on such micros would be applicable.