It doesn't make much difference potential wise.
If you already have let's say 200% luk.. it's better to just pump up luk then str or dex.
for other jobs, pure stats is better but for xenon, pure stats means 1/3 of what could have been added to your range.
allstats % is what u need for xenon. which makes sense considering the link skill from xenon is also 10% allstatsthen 150% luk/str/dex)