Look bro- I'm not McClain advocate, but he's better than Brady on any day. Ponder this- if they both came out of college the same year, who would you take? I think the answer is easy.
I agree with you that McClain, when playing at his peak, is a much better player than Bradie James playing when he was at his peak.
The question with Ro is how often does he feel motivated to play at his peak? How often does he feel motivated to practice? How often is he going to pull himself out of game?
Bradie James was a lesser talent -- he was never better than a average 3-4 ILB.
What you can say about him is that he showed up (96 straight starts at one point) and he was consistently productive (averaged over 100 tackles per season from 2005-2010).
McClain 5 years into his career has never broken the 100 tackles mark. I'm sure if you asked him he would tell you all the reasons why it's everyone else's fault too.
Coaches deeply favor guys who show up and play consistently. Coaches hate, no despise, players who they can't count on for consistent effort. Look no further than the Cowboys making zero attempt to resign Bruce Carter despite Carter leading all NFL linebackers in interceptions last year (5 of them).
My point he is it is very easy to fall in love with player's peak performance as opposed to their 'typical' performance. I'd argue, that in the end Bradie James productivity and consistency, over the long run, will make his career much better than McClain's