it doesn't matter what the gun is, it's how you use it. I've seen members here with photos of them competing in 3 gun with a k98 mauser.
you could just as easily train yourself to load a $235 sks with stripper clips as you could train yourself to change mags on an FAL.
as for low cost alternatives. the only gun that you listed that is cheaper than the AR15 is the SKS, now that obama gun grab 2013 just came to a screeching halt demand for 223 is going to go back down and soon after prices will fall back to pseudo-acceptable levels.
all guns lost in a tragic smelting accident.
I never said half the crap people said I did-Albert Einstein
You can't believe everything you read on the internet-Benjamin Franklin
Bean counters told me I couldn't fire a man for being in a wheelchair, did it anyway. Ramps are expensive.-Cave Johnson.