Re: Justice League Vs Avengers
First off any one side could win given the right story line. In my honest opinion I think that JLA are way more powerful not only in terms of powers but also in terms of personality.
This all comes down to Team work really and JLA work really well together. There able to change tactics very quickly with very little effort, especially when Martian Manhunter links there minds together so they can communicate with one another. Often times JLA will realize something there doing isn't working and suddenly change tactics in such a way leaving the enemy caught off guard.
Which brings me to my next point and that is tactically abilities. Batman of course is the JLA greatest tactical thinker and can analyze a fight and come up with solutions in the heat of combat, this works there favor even more so by Martian Manhunters ability to interlink there minds so they can communicate with one another. While Superman and Wonder Woman are not on same level as Batman as far as being tactical thinkers they are not to be underestimated either.
In the end it is those two factors that give JLA their greatest advantage. There are few things I'd like to point out.
1.) Quicksilver is no where near as fast as Flash, don't know why they keep letting Quicksilver beat Flash. The Flash has been shown to move so fast that he can travel through time, Quicksilver has never been show to be able to do this as far as I know. So no way is QuickSilver faster then the Flash.
2.) Thor can move faster then Superman just not in same way. Thor can travel at speed of light. He can also travel between dimensions. However they have never shown him to really use those abilities during combat at least not in same way Superman or Flash might. An example Superman can hit an enemy from different directions and it seem like he doing it all at once, when really he moving so fast you just not see him going at his target from multiple directions, same with Flash. Thor has never been shown to do this.
3.) Thor hammer was magically created but when he throws it and it hits something it's physical damage. So Thor is really going to have to hit Superman really friggen hard to seriously hurt Superman.
4.) Thor doesn't posses the same Strength as Superman. Superman can bench press the earth for give days before he even begins to show the slightest sign of exhaustion. Read Superman issue #13. As far as I know Thor can bench press the earth even once let alone for 5 days.
5.) Yes Thor can summon lighting with his Hammer but he can't magically create it, thus it will do very little to Superman other then annoy him. Basically here is difference, Storm can summon lighting almost in same manor that Thor does but its not magically created lighting it's summon lighting. However Captain Marvel can magically create lighting by saying Shazam and it will hurt Superman. So really Thor would only be annoying Superman more then hurting him.
6.) Yes Hulk could reach a point where he could defeat Superman however at the onset of a battle he does not have the mojo to defeat Superman. Superman might not be on par with Batman as far as tactical thinking but he is not an idiot either, he can quickly analyze a fight and find weakness and use them to his advantage. In short he would realize the longer he fights hulk the more powerful he become and thus he would shut Hulk down fast.
At the end of the day my money would be on JLA. I think they work better as a team and I think they have a bit more power under there belt. That is just my opinion anyway. However as I said it all comes down to story line. With the right story line even the weakest hero or villain can beat the most powerful villain or hero.