I think you will find they are both good companies,The Sustain from shimano is worth the dough as is the Stradic MGFA,You may even want to check into reels like the quantum p.t. catalyst.It boils down to really how much you want to pay and then compare what you get bearing ,etc wise.I cant vouch for Okumas customer service,or quantums,but I know Shimanos customer service has been great for me and has gone to extra lengths to help me with my reels.
tight lines,
brian