I do like the PSO2 style drops, and it works out alright with 4 people, as far as my calculations went with the 70% overall drop and the 50% rare drop rates taken into consideration.
As long as the drop rate isn't really higher than around 1/1.58, the chance of
at least one dropping is higher. I did the math (red is 4 people on PSO2 drops, green is classic; higher is better):
http://puu.sh/kArHf/cf65e74e4c.png The difference between the two does peak around a 1/3.3 drop rate, and become less than 1% around 1/38. Still, keep in mind that
there is the chance for multiple to be dropped, so if you're playing with three close buddies hunting for something, this is still probably your best bet if you want more than one.
It had been a while since I did some decent algebra, so it did fry my brain a little bit.
Maybe I'll go through the 2P/3P calculations later. Also, I did not calculate in lucky day bonuses.