"Can't decide" is a lame option. Either you like Bros. Attacks or Items more, If you can't decide think long and hard.
I voted attacks. While not as versatile or variable as items, they look cooler when used and go along with the game more sensibly--it makes sense that you'd be unable to do Fire Bros. at the beginning simply because they haven't learned how. The old-fashioned "Oh, yeah, we won't get any orders of the most powerful item until later in the game and no enemies around here will have them" rule just isn't as realistic. Also, the Advanced versions are awesome.
Okay, the Copy Flower was cooler than any other Bros. Item or Attack. It's also super-powerful when mastered...But the first time I got Advanced Thunder Bros. right... oh man.
Fifth: Well, you get eternal Bros. Items with the Ulti-Free badge, which is kind of cheating... though you have to work your butt off to earn it so it's fine with me.