Use the search function. This topic comes up about as often as .45 ACP vs 9mm and 1911 vs Glock. There are literally dozens of threads on exactly the question you just asked.
Here is just one I answered just a few weeks back
http://thehighroad.org/showthread.php?t=482655&highlight=fal+m1a
Other than price what is the difference and which would be the best to buy?
You will also see that it comes down to personal preference. They are all good rifles and there is no "best". It's like asking "what is best...blondes, brunettes, redheads". All comes down to personal preference.
...and by the way, the answer is clearly FAL. But not just any FAL...either original Belgian or DSA. Don't waste your time otherwise.
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Here's a cut and paste answer
Cold War Battle Rifles
M1A
Pro
Reliable design
Full power cartridge
Very comfortable (for most) stock
Can be quite accurate
Great sights
Safety is convenient location in trigger guard
Con
Scope mounting is awkward over the receiver
Field stripping has lots of part/not straightforward
Can't be cleaned from chamber side with a rod
Expensive mags
FAL
Pro
Reliable design
Full power cartridge
Extremely good ergonomics
Cheap mags
Extraordinarily easy to break down, field strip, clean
Adjustable gas system
Con
Sights are adequate but better A2 style sights exist
Triggers not known to be great but they can be improved
Not quite as accurate but certainly within battle rifle specs
HK91/G3/PTR91
Pro
Reliable design
Full power cartridge
Cheap mags
Somewhat easy to break down, field strip, clean
Can be accurate
Con
Sights are adequate
No bolt hold open
Abysmal ergonomics - safety selector is near impossible to reach, cocking handle is in terrible place, mag release is hard to reach
Triggers are absolutely horrible but they can be improved