IIRC max LP mult between NS and HS is 3.25(for syndicate systems vs a 1.0 HS). That means at most you get 3.25 times more LP in null sec than in HS, for the same mission.
The highest mult in HS (compared to the worst) is 1.87 for lanngisi, meaning a 1.74 mult between 98q and Lanngisi.
then of course you should also note that the LP worth can be better in null than in HS.
Thus I just ran the number, for both average daily and direct normalized LP worth.
Average value, NS is 10k isk at best, and 3.8 in HS at best, meaning a mission that nets you 20M isk in LP in Villore would net you 52M isk in LP in N5Y (2.6 mult).
Direct value, NS is 7 in n5y while HS is 2.7 in gelfiven. (2.6 mult too)
What that means is that if you can make missions 2.6 times as fast in HS (because geography, because officer modules, because implants you could not afford to lose in NS, because less roaming ganks, because you can dual box missions without having to press V every 5s) then it’s not worth to go in NS.However this only takes into account LP worth, because direct isk worth is 1.74 times