the way I see it is as follows:
1) No Gadgets for either side, ie, goblin doesnt have his glider, joker doesnt have other items he is commonly seen with
-Joker has human level durability, reflexes, strength, ect whereas goblin has enhanced
-Joker may have an edge is fighting ability, considering he fights batman, but Osborne has enough of a reflex and agility bonus to just be too fast for him.
-Give them basic weapons, like bombs, grenades, guns bats lazers ect. and I still give an advantage to goblin. Joker cant move nearly as fast as Spider-man and he has trouble dodging a barrage of pumpkin bombs.
2) Give them all of their weapons/gadgets
-I'm not sure what this means for Joker? But the Glider for Osborne is a HUGE advantage in this fight. To compete with that and his arsenal, I dont know what the joker is going to be able to do, seeing as he might as well be standing still on the ground.
3) Give them prep
-Both are obviously criminal geniuses, brooding and paitent. Both stalk and get knowledge of their oponents. In this regard, I think they both would probably have some very effective prep time.
-Osborne is a millionaire with knowledge in science and engeneering that rivals people like tony stark. His resourses for plotting a proper defeat of the Joker would be enormous. What does the joker have to contend with this?
I dont think the example of Joker beating the JLA is PIS, in fact, I think it just shows in general how one sided prep can make a fight. Obviously, if he is given enough time to stalk and prep for a fight against the goblin, Joker will dominate. But its not fair in any circumstance to only give the one side prep time, because it allows them to generally exploit the single weakness of the stronger opponent regardless of any other considerations. To be honest, given what is known about Osborne and his capabilities, I wouldn't be suprised if he could PIS a win off against the JLA in the same way that Joker did.
Joker with prep, 8/10
Both with prep, goblin 7/10
gadgets, goblin 9/10
no gadgets, goblin 10/10