This is a bit of a deceptive question -- the more you know, the more it will irritate you! The *chemical* properties can follow the group (stoichiometry of reactions, to some extent energetics as well).
But the physical properties -- the best you can say, is that the elements may vary MORE across a period than they do down a group. Consider N, P, As, Sb, and Bi -- these range from a gas vaporizing at 63 K to a metal melting at 544 K and vaporizing at
1837 K. You wouldn't call these similar, EXCEPT by comparison with a period: say, Li to F, with C melting at 4100 K !