personal experience...if the rims are silver, the brakes won't grab as fast. they'll lock up, but not fast enough to pull like an abubaca or a fufanu for most people. silver rims are good if you need to feather the brakes during a manual or something like that...chrome rims will lock up faster than silvers, unless it's raining. i assume that when "chad smith" says "alloy," he means silver and not chrome....of course most rims nowadays are made out of some type of aluminum alloy, so maybe he means chrome...i don't know. he didn't say.
i wasn't saying anything bad about U-brakes. i love them, except they're hard to adjust.