Pierzynski is clearly the more attractive of the two options, reputation aside. Texas' biggest hole is clearly at catcher, where the Rangers have Geovany Soto, Luis Martinez and Eli Whiteside on the 40-man roster. Pierzynski had one of the best years of his career in 2012, hitting .278/.326/.501 with 27 home runs for the White Sox, while providing slightly below average (read: adequate) defense.
Though Pierzynski will turn 36 in just over a week, he remains a very solid catcher, and could provide the Rangers with much needed offense, at a position where the Rangers, as currently constructed, have very little. Giving Pierzynski a three-year deal would be a mistake, but a reasonable case can be made for giving the free agent catcher a two-year deal.
Ross, on the other hand, is a player the Rangers should aim to avoid -- unless they're planning on platooning Ross and David Murphy. Between 2010-12, Ross hit lefties to the tune of .276/.352/.530, with 21 home runs in 355 at bats. Against righties, Ross hit a meager .254/.315/.402, with 29 home runs in 1,051 at bats.
Suffice to say, Ross should not be paid like an everyday player.