Let's take Pennington's career year, 2003, and make a breakdown of his passing numbers.
During 2003, he threw 89 passes behind the line of scrimmage, and he completed 71 of them. (71/89, 80% completions)
From 1-10 yards, he threw 147 passes, and completed 115 of them. (78% completions)
From 11-20 yards, he threw 96 passes and completed 61 of them. (63% completions)
From 21-30 yards, he threw 31 passes and completed 9 of them. (29% completions)
From 31-40 yards, he threw 12 passes, completing 2 of them (17% completions)
He threw no passes beyond 41 yards.
Looking at Pennington's stats (he had a total of 399 passing attempts that year), he attempted 43 passes beyond 21 yards (or what most people would term a deep pass)(I am using the term loosely), so out of his total attempts about 10% were deep passes.
Now, comparing that to passers such as Tom Brady (generally known as a dink and dunk, west coast passer) and Drew Bledsoe (who is widely known to have an excellent deep ball), Pennington did not throw nearly as many deep passes. To back this up statistically, Brady attempted 62 passes beyond 21 yards, and this amounts to about 11% of his total attempts (527), while Bledsoe attempted 156 passes beyond 21 yards, and this accounted for a whopping 33% of his total attempts (471). Additionally, Bledsoe attempted 5 passes beyond 41 yards, while Pennington threw none. It is evident, that Pennington's passing profile clearly resembles Brady's (a west coast passer) as opposed to Bledsoe (a deep-passing game QB).
For kicks, I compared the completion percentages between Bledsoe and Pennington in passes from 21-40 yards. Bledsoe's completion percentage came out to 27% (11/41). Pennington's came out to 26% (11/43). Judging from the comparison to Bledsoe (to reiterate, he's widely considered an excellent deep passer), our boy Chad isn't that bad of a deep ball passer at all, and in truth, he really didn't attempt THAT many deep balls anyway.
*All stats are from 2003, to keep things consistent.