As said, there's definitely a perceivable difference between the three, and I imagine even more so with a long haul like 50ft.
For good to great cables at bargain prices, check out
www.bluejeanscables.com and
www.monoprice.com. I've personally purchased speaker cable from BJC, and I can say it is excellent stuff (Belden cable is known to be good). However, it's not exactly cheap, particulary video cables, but you can purchase custom lengths. I believe their stuff is about as good as it gets in such a price range. Monoprice, on the other hand, is well known for good products at low prices. For an alternate to Monster Cable or Acoustic Research (i.e. Best Buy, Circuit City), I'd shop there.
BJC would cost over $100, so I'd suggest this:
50Ft 3-RCA Component Video Cable (RG-59/u) $14.50
OR
PREMIUM 50FT 3-RCA Component Video Coaxial RG-6 18AWG 75Ohm CL2 Rated Cable $38
For that length, I would personally go with the higher grade RG-6 cable.