Originally Posted by
ducklord
For the full classic bronze age JLA, you've basically got:
Superman
Batman
Wonder Woman
Green Lantern
Flash
Aquaman
J'Onn
Hawkman
Atom
Green Arrow
Black Canary
Elongated Man
Red Tornado
Hawkwoman
Zatanna
Firestorm
Phantom Stranger is an odd duck. He was officially offered membership (as opposed to some auxiliary members like Batgirl and Metamorpho), and he never turned it down (like Black Lightning did). He even showed up when summoned by the JLA communicator on a few occasions. I like to include him, but it's probably a more legitimate argument that he shouldn't be.
For the JSA, up until the Crisis you've got:
Flash
Green Lantern
Hawkman
Atom
Dr. Fate
Spectre
Hourman
Superman
Batman
Wonder Woman
Starman
Wildcat
Mr. Terrific
Johnny Thunder
Black Canary
Robin
Star Spangled Kid
Power Girl
Huntress
Although the JSA has a few more members than the JLA, they are overloaded with "regular guys in masks" - Batman, Huntress, Robin, Black Canary, Mr. Terrific, Wildcat, and Sandman. Even accounting for the Atom's later atomic punch, that puts them at a disadvantage.
Where the JSA has a clear advantage is in magic. Between the Spectre, Dr. Fate, and Johnny Thunder, they've could wrap up a battle with the JLA in seconds on their lonesome. Zatanna and the Phantom Stranger are powerhouses in their own right, but they don't measure up.
If you're willing to call the duplicates a draw (just for the sake of argument), then the JSA has advantages in numbers on a few fronts. They've got a Batman, a Robin, and a Huntress to counter the JLA's Batman, as well as a Superman and a Powergirl to take out the JLA's Superman. The JLA has an advantage with two Hawkpeople to counter the JSA's singular Hawkman.
The JLA's clear advantage is in variety. They have a stretchy guy, a guy who commands sharks, a shrinky guy, a guy who shoots arrows, a gal who screams real loud, an android who creates tornadoes, a telepathic stretchy guy with near-superman strength, and a kid who can alter fires atomic blasts AND can rearrange molecules if he's given a few seconds to think about it. All the JSA has left in the tank at that point are couple of guys with (admittedly bitchin') cosmic rod technology, and Al Pratt's atomic punch.
Basically, if the JLA can somehow stop the Spectre from turning them into rubber ducks and rip off Fate's helmet, the JLA probably wins in a walk.