If they fold and you have the flush, technically you didn't win using a royal flush. That way you can go all-in every round without worry

I'm surprised that the percentage choice was so much greater for super-strength. Super-speed would be way more useful to me in everyday life and allow me to accomplish all sorts of extra things. When do I ever find myself needing to bench-press more than a few metric tons, on the other hand?

It could be argued that super-strength would make your legs super-strong, allowing great speeds. Not as good as the Flash, but still pretty fast. The Hulk is a good example of this.

UP YOURS RUSH HOUR TRAFFIC!
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Herp. Derp. I is strong. Derp. I broke the toilet.
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No, super strength doesn't allow super speed. STR and DEX are separate stats. Duh! :P