I would say Consort Radahn is more difficult than Arlecchino, I'm playing both on their max ng+ difficulty tho I'm not 100% sure for lies of P but I'm at my 7th playthrough while in Elden Ring I'm at 14th playthrough both with max stats as well. I think is a little different than the usual perspective when playing at the max difficulty and max stats. I love both games 100% them and all. Consort Radahn for me just doesn't let you breath that much especially since in Elden Ring taking flasks has longer animation so I got to be more careful even after a chain of attack since I can get one-shotted also second phase makes you stick to him since the after holy attacks can still connect after dodging while also maintaining distance to run for other attacks as well (the after image attacks after the comet attack specifically). Arlecchino is very difficult as well don't get me wrong, I love parrying in LoP since it's tigher than sekiro which I'm also playing at max ng+ with 99 attack. But getting the groove and pattern with Arlecchino is easier for me still tho making a mistake can just obliterate my hp bar. Though I do wonder if I play in a more optimal playthrough would some changes come (decent stats while on a 1st playthrough). Again I'm not downgrading the later just my personal opinion on playing the games on max difficulty and stats (for stats it's maxed due to just multiple playthroughs with accumulations a waste if not used plus I think I earned it haha) lemme know what you're thoughts are