Global ES or shield ES?

Hi there!

I have some questions about the build that i am doing for my shadow.

Here it is :
http://www.pathofexile.com/passive-skill-tree/AAAAAgYABfkNfA5IEHsRLxGWFfAWvxzcIuonqSj6KgsrCizhPs9HBlFHVvVXyV3yY0NqjG1scFJwVnDVd_1943_GidOOipAbkyeX0JmamhObJp2uotmly6Z_pwinNKxmsNixs7QMtUi297iTuT695r46wcXIFM3q2HbbGttu29TesOcL51TndOjW6rrrY-vu7UHy4fPq9W_2_Plj

My question is,should i upgrade my global ES like putting the skill nodes in the 6% more ES or should i put them on the 30% more ES with shield?

What is better,i want to have the "max" ES possibel but i am confuse in what should i upgrade,cause if i upgrade my ES with shield i will remain with my shield,if i upgrade my global ES i will have dual wielding.

Thanks

Sorry for my bad english

Even if you have a shield equipped the global ES bonus is better than shield specific ES almost without exception.