I'm not a gambler, so I'd rather drop my dough on a great flight experience.
My first flight on VX was F and I was sold from then on.
I'm not a fan of the food in F, but that is a matter of taste. The rest is great. I rarely sleep on planes, but enjoyed a nice cat nap on the way to LAS.
You could try and score MCS on a last minute upgrade and that is not expensive at all.
Bon voyage!