This is my experience with b-stick versus c-stick.
I learned about b-sticking before I purchased Brawl so I have been using this setup for Lucas for a month or so. Of course, I found that using the b-stick made spacing with pk fire a breeze. I also discovered that b-sticked psi magnets were amazing for off-the-stage spikes and magnet infinite edge-stalls. I also owned a ridiculously old gamecube controller with no up/down smash functionability and so I learned how to pk thunder with the bstick. The b-stick allows for an amazingly intuitive control of Lucas's special attacks.
Initially, the people I played against were swept away by the ferocity of Lucas's tricks. The pk fire spam was especially harrowing for my friends. However, like all good players, they adapted. And quick. They learned to avoid the attack through hearing, since there is a slight delay in between Lucas saying the first part of "PEE KAY FYE-UR" and the attack actually coming out of his hands. Little by little my wavebounce advantage was demolished as they short hopped fast fell air dodged to approach, attacked the bolt head on, or SH jumped over the buggers entirely.
I was not a strong melee player. I am not a strong melee player. I am a melee scrub. Having defeated all of my friends in middle school, my shiek was shelved during high school after losing to a Peach played by a guy on the football team. I hold no strong feelings for melee but I see now that I should have learned the basics of character movement before giving up the stuff. I didn't even c-stick for pete's sake. As a result, my Lucas suffered from stilted aerials and perpetually inaccurate fsmashes.
I reviewed my playstyle and concluded that I needed to learn how to c-stick my aerials before b-sticking burned itself into my muscle memory. So I changed things up.
Immediately, I became a more offensive Lucas. As someone mentioned before, b-sticking lends itself to a more defense-oriented style of play whereas c-sticking is the complete opposite. I was actually consistently getting kills on characters at or below a hundred percent. Most of this was due to the amazing discovery of c-sticked bairs. No longer having to rely on occasional pk thunder gimp kills and difficult magnet spikes for below-100 kills, I began widening the stock gap between my opponent and myself from one to two stocks (occasionally three stocking some people who were still used to my defensive camping). Of course, the fast fmashes (very noticeable against quick foes) and appropriately timed dsmashes helped as well.
I have also come along in terms of spacing. C-sticked aerials are amazing for spacing, especially when your opponent is used to approaching nairs and shield-grabs through them all the time. The most amazing aspect of c-sticked aerials that I’ve experienced so far is the increased likelihood of baiting the opponent. Whereas b-sticked pk fire is both an offensive and defensive tool, spamming the move stalls the game and doesn’t really open up any approaches for you or your opponent. A smart foe won’t rush in blindly, get nailed by a fire, and be punished for it. They will approach carefully and IF they get hit, then chances are you will be recovering from the small landing lag on the pk fire and won’t be able to follow up with anything fast enough to really make them pay. Maybe they will get hit just to see how you will react, who knows. I know that c-sticking a fair/bair can have some devastating consequences if it hits AND still provide enough spacing to be tricky to punish if it doesn’t. I believe a c-sticked aerial is a b-sticked pk fire with greater risk/reward.
I have come across two techniques in the tactical discussions board which make c-sticking (or even tilt-sticking) even more appealing; true pivot and pivot fmash. Both accomplish the same goal as spacing techniques, though the latter is more limited. I suppose you can even pivot dmash with the former. Both techniques are most effective using a c-stick setup as opposed to a b-stick setup. I am trying to incorporate them into my play.
True Pivot (by phanna):
http://smashboards.com/showthread.php?t=162220
Pivot fmash (also by phanna):
http://www.youtube.com/watch?v=2X9oqJEXYMM
Feel free to disagree and explain how b-sticking is all sorts of pwnsaucedeluxe. I am still learning.