I'm going for Metzler myself shortly. Mostly on price as they are almost half the price on the stock Dunlops on my UC. I have heard good things about them though.
I'm a big fan of the Metzlers. I have not used the E3's but heard good things about them. Metzlers will wear faster then the Dunlop 402's but handeling is much better with the Metzlers.
I have heard good things about both. I am going with E3's. Dunlop is made in the USA. Last I heard Metzler had a plant in Brazil. I seem to remember some trouble with quality?? Could be just urban legend though. I figure all in all I will try an spend my $$ on American made products.