23-9 will be easier to pedal but you will get less speed, 29-9 would be harder to pedal but you would be able to go faster. I run 28-9 and I'm pretty stoked on it.
28-9 on lower gearing i find going big scarier because you know your flat out, on stiffer gearing you feel like your hitting stuff slower because your pedaling slower (both going same speed) hope you understand what i mean