echo doesn't need parentheses around its argument(s) (it's not a function) - and if it has more than one argument (unlike print(), it can take more) it _mustn't have parentheses. It's also equivalent to the '=' in the <?=$variable?> HTML-escaping idiom.
print() is a function and does need the parentheses.
print() also returns its argument, so you can say $output=print('This is a string I just printed out.');, but why being able to do that might be necessary is anyone's guess.
So yeah, like Ben says, do whatever turns you on. I always use echo myself, but that's just a habit.