Its all relative...with flywheels, depending on your setup but in most NA cases, lighter is better. Whatever is lightest is the way to go, which in most cases means aluminum.

Fidanza is great @ 7.5lbs, and from what Ive seen of the ACT flywheels, theyre very nice and super cheap as well.

In terms of weight, its important to find out not only how much it weighs, but where that weight is distributed. Thats what counts. The Fidanza's design is great, as well as Toda if I remember right.

The problem with Toda is that youre paying for:
A)the name
B)Chromoly steel which isnt ideal IMO

Id go Fidanza personally.