First, the different ways we define our respective terms creates a huge impediment to constructive dialogue. Even after coming to understand what a Catholic means by "justification" (i.e., something akin to what Protestants would call "salvation"), I still find myself forgetting momentarily and arguing in a way that totally misses the point.
Secondly, both sides make similar claims about their views. For example, Catholics and Protestants both affirm that salvation comes to us by God's grace alone, and that our works neither merit nor cause salvation, but only flow from it.
Now when heard with Protestant ears this claim on the part of Catholics sounds, prima facie, utterly false and even laughable. But when account is taken for the differences of nomenclature, and if and the Catholic position is allowed to play by its own rulebook and use its own lexicon, it certainly appears internally consistent and even gracious.
That said, however, there still remains the issue of how terms are defined and, more importantly, how texts are exegeted by both sides. So while I will concede that, given its own formulations, the Catholic view makes sense, Catholicism's terminology and the exegesis on which it rests are, at the end of the day, inferior to that of confessional Reformed theology. Whether the issue is how we define justification or how we exegete the early chapters of Romans, I humbly suggest that historic Protestantism carries the day.
Of course, depending on how we answer the "authority question," this may all be completely beside the point....