Matt i have been in your situation and can tell you that a stock bike is superior to 20" and 24" in lots of ways. Taps, ups, gaps, sidehops are all easier on a stock. I also honestly believe you can go higher and further on a 26" than the other two aswell. I can see there being a niche in trials for 24" tgs geo frames as there are people who 'think' there too small for stocks and too big for mods or just don't like either but if you want the 'best' bike for tgs type riding 26' wheels are the pinnacle. ( Opinions based on having all of the above plus considerable amount of time and practise on my because 24 )