The reason I think it's not splitting hairs and it's worth discussing is because some try to act like Walt didn't have an arc. The show was Mr Chips going into Scarface. It wasn't he's a monster and was always a monster. I think that's a lousy way to view the show.
The origin of this discussion was this post and it's follow up reply
I agree with Veelk and I don't think Vagabundo's view here is a good way to view the show.
It does make a difference whether someone is a bad guy (Walt in Season 1) and a monster (Walt at the end).
Totally correct. This issue was describing Walt as that in the beginning.
I've thought about this some more as I've continued rewatching the show (started s3 last night) and what I'll say to this is I don't think Walt changes much, I think it's mostly the circumstances surrounding him that change. The stakes keep escalating but he's fundamentally no different than when he started, he just hasn't had the opportunities at the beginning that he gets later. From the very beginning of the show he hates his domestic life - he likes the ideal of being a family man because that's what he thinks masculinity is all about, providing for your family no matter the cost (even if that cost is, ironically, the cohesion of the family itself). But any time anyone questions him or holds him back in any way or he has to display some empathy, he balks and retreats to where he can feel like a big man. Dude has zero self-awareness about just what a piece of shit he is, a thing that the S3 premiere demonstrates wonderfully when he downplays the plane crash to anyone and everyone. He has no empathy at all. The entire show up to this point is a cycle of Walt doing shitty things and feeling sorry for himself afterwards. It's actually really tiresome, I think this show's kinda boring half the time because I am tired of seeing Walt go through this "exercise" as Chuck called Jimmy's cycle of remorse in the BCS finale. It feels like repetition. The domestic scenes keep following the same pattern too, between Skyler and Wal't arguments.
The difference between the shows is that BCS has much better characterization of all of its leads than Breaking Bad, which fails to invest anyone but Walt and to a lesser degree Jesse and Hank with the kind of complex and nuanced internal life to make us care. Skyler is right about everything all the time but that doesn't make her likeable or all that interesting, and this is a failure of writing.
This is kind of rambly, but the TL;DR is that Walt is a self-righteous, self-pitying sad sack from beginning to end, it's only the external circumstances that change and bring out who he was all along. Whereas I think Jimmy>Saul is actually a transformation brought about by the conflict between him and Chuck and eventually the loss of Chuck and (we assume) Kim, and I think there is MUCH more meat on those bones in terms of moral and psychological nuance.
Very well put (and accurate) statement by AMC, as well. 
