@WBYeats,
Actually, I'm not sure either is strictly appropriate if you are intending to be polite.
If someone injures himself, you might say "Better you than me".
"Age before beauty" sort of implies you are giving some priority to someone because they are old.
If someone yields to another saying age before beauty, the standard response is "Pearls before swine", and go right ahead with whatever you want to do.