Fluidmaster 400a vs. Korky QuietFill

I recently replaced an old-fashioned valve with a Fluidmaster 400a, and I notice that it shuts off very abruptly. It causes a "thump" when shutting off. Granted, the noise is not very loud but I'm wondering the abrupt shutoff might be bad for the pipes.
Another toilet happens to have a Korky Quietfill (actually under the old "Hunter" name). What I like about the Hunter is that it shuts off quickly but it does so in a much smoother manner.
Only problem with the Hunter that I've had so far is that ONE time (in the year I've been living here) the valve did not try to fill up the tank after a flush and was instead simply making a slight hissing noise. When this happened, I gently tapped the side of the valve's top enclosure with my fingers and then it filled up just fine and this never happened again. (the float must have somehow gotten stuck, and I don't know why)
I'm just wondering what the overall consensus is as to which of the two valves is better, and lasts longer, etc. The abrupt shutoff on the Fluidmaster 400a concerns me a bit, although I don't know if it really a problem.
Another question, how long do the flexible supply lines typically last? Do they need to be replaced after a certain amount of time to prevent bursting?
J.
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http://www.fluidmaster.com / is my favorite manufacturer for toilet parts for 20 toilets i maintain. flusher fixer ends leaks from tanks. there is no damage to pipes by an abrupt shutoff of any water valve. flexible supplies have lasted indefinitely, would only need replacement upon failure like from freezing.
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<<there is no damage to pipes by an abrupt shutoff of any water valve.>>
Will there be no damage even if I'm hearing an audible thump (pipes vibrating) when the Fluidmaster shuts off?
Thanks,
J.
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