To look at the obvious stats, there is little comparison between Johnson and Pomeranz:
Johnson IP's 69 ER's allowed 27 ERA 3.52 K's 64 BBs 22 WHIP 1.42 BAA .269 HR's 9
Pomeranz 51 " " 36 "" 6.31 K's 44 BBs 32 WHIP 1.81 BAA .299 HR's 10
Draw your own conclusions about who has the ability to get it done with their skill level