The only advantage of Mugen exhaust manifold is the cat, you wont need to worry about MOT.
Power gains wont be as good as a full race exhaust manifold.
Toda is the best one.
Compare to Toda, Mugen cost 133000 Yen more, which is nearly twice as much as Toda Manifold. Hmm.... need to reconsider now... seems stupid to buy Mugen...