Which one is the better of the two cables. Monsters packaging says that the fiberoptic is better. But some people have told me that the coax makes a better (tighter) conncection.
In my opinion optical is better. With wire you will always have the possibility of EFI (Electro-Magnetic-Interference). With optical EFI is impossible. The downside to optical is that they are pricey and fragile. If you put too much of a bend in one you are likely to break the fibers.
There is basically no difference in sound. I prefer coax, and EMI is not a problem with a good cable. I've been using coax for years with no interference of any kind. If you don't have anything to generate EMI or RFI in large ammounts near the cable, neither is an issue. If it was, it would already be an issue for your other analog connections.
Tight connection? RCA is a more positive connection than optical, but tightness really doesn't make much difference to a digital connection.
Optical cable is not expensive at all, they can be had for as little as $9 for a 3ft cable, but they ARE fragile.