Walker's peripherals are much worse than his ERA based results indicate. His FIP is fine/average but his xFIP is poor, his command has been iffy with the Blue Jays and he's been walking a lot more. Shoemaker has been beat up by the longball but aside from that his peripherals are pretty good and his sample is pretty small anyway. There shouldn't really be a preference of one over the other, they're not the guys you want starting short series playoff games anyway and I imagine both will be on extremely short leashes unlike Ryu.