Single or dual cats?

[margas]

What would be better?
1) Single 2.5" cat (Magnaflow 59926) with Ys before and after.

2) Keeping the pipes separate with dual 2" cats (Magnaflow 59954)?

What are the advantages/disadvantages?

The car is a 325i, exhaust is stock (new muffler) and the only engine upgrades I have are a chip and cam. Thanks!

[nando]

since it's all stock a single 2.5" would be better, cheaper and lighter.