Which differences exist between EVA4400, EVA6400 and EVA8400?

Which differences exist between EVA4400, EVA6400 and EVA8400?

A.
EVA6400 and EVA8400 models have dual controllers.

B.
EVA6400 and EVA8400 models do not have Array Management modules.

C.
EVA6400 and EVA8400 models do not have loop switches.

D.
EVA6400 and EVA8400 models have user expandable ____________.