P and K Geese are always debated, but I think imo that K Groove Geese is better than P Groove Geese in the arcade, and on XBL P is better than K, if only because of the super cancel. If you're able to land a jump in attack, they can be prepared to eat over 11k damage from cancelling the last hit of a Jai Ei Ken into a level 3 Raging Storm. You could always go substitute the Deadly Rave instead, and cancel right before the last hit of the Jai Ei Ken, and instead of finishing off with the qcb+hp, you can just hp xx mp version Jai Ei Ken. It'll dizzy, and then it sets up for another bnb Geese combo.
That's why you'd want to use P online. That super canceling is just wrong on so many levels. K is still good because his counters add to his meter, and give big chunks. He has great poke strings and a godly cross up (jump mk) that it's almost illegal to not use it. When Geese is raged, you can almost guarantee a guard crush and a deadly rave followup.
I still think N is his best all-around groove, though. Best anti-air is his crouching FP. Great to pull out whenever you think a person is baiting a counter. Just watch out for jump in parry/jd, but then again you could always bait those and then it becomes one big mindfuck game. He has his run, his guard-cancels, max mode which benefits his poke strings + extra damage, small jumps (love that crossup mk), and safe falls.
I only use two bnb combos, which are:
c.lp x3, c.hk, xx repukken
Crossup mk, c.lp, c.lk, c.mk, xx repukken/deadly rave (use this one the most)
You can't really give strats on counters, other than to read your opponent as well as possible. High counters take out jump ins, specials, and supers (non-grab/fireball). Almost always opt for his crouching FP to hit people out of the air. His standing HK is ok, but hard to time, especially if your opponent is mixing things up.
Geese has a hard time with people who have really fast jumps/small jumps, like Mai and Blanka (at least for me). Fucking bastards.