another galapagos q! 8d cruise north/west or east/central/southern?

hi

(sorry if this has been asked before),

if i have a have a choice of doing an 8D galapagos cruise - do i choose from a western/north or an eastern/southern/central one?

my aim would be to see the maximum variety of wildlife and natural features: and perhaps later do some accessible land based trips on areas i did not cover on the cruise.

also, can anyone recommend a travel agent in puerto ayora who deals in last minute cruises and do you barter on their asking price?

thank you for any assistance you may be able to offer