I am, and will always be a fan of Kane first. Ironically, I was always a huge Undertaker fan, but when they started to introduce Kane, with the entire backstory they set up, and how impactful his debut was by ripping the door to the cell off its hinges, and his overall look turned me into an instant Kane fan.
I never stopped liking Undertaker, but I immediately became a huge Kane fan, and haven't stopped being a huge Kane fan ever since.
I think at his peak, Kane was actually a little more agile than Taker. He was able to do things that I've never seen Taker do... spring board body splashes, spring board clotheslines, hurricanrana's, drop kicks, etc. In the long run, Kane has bad knees and now isn't what he used to be. He can still work decent matches with the right match type or opponent. Taker has slowed up too, and he's more limited in his aerial attacks and agility now than he was, but he hasn't slowed to the point that Kane has. So, right now, ring wise, Taker's better. However, I think Kane's better with the mic if given the opportunity.
In the long run, it doesn't matter. What has EITHER of them done in a long time that's been noteworthy? Vince has been using Kane and Taker to job for years to new guys breaking in to the industry... and the killer part is, they do the jobs to put guys over, and the guys they put over never even amount to anything, yet... every year, we still see WWE pulling new guys out of their asses to throw in there with Kane and Taker and after their fued with Kane and Taker is over, they amount to nothing.
Kane's fueds that amounted to nothing...
Remember Snitsky? What happened when he fueded with Kane? He was at the top of the card, now where is he? Kane spent months locked up in a fued with him and WWE wasted months of building Snitsky up as a legit force, and then after all that, WWE decided to just drop the ball with Snitsky, therefore... it wastes Kane's time.
Fake Kane? Another new guy and I shouldn't start here... a new guy randomly brought up as a fake Kane. Kane does the job to the new guy, and then because of crowd reactions for the one PPV night, WWE dropped the entire angle.
MVP? Sure, MVP's being pushed now... but so was Snitsky... only time will tell.
Undertaker...
Dudley's? Heidenreich? Great Khali?
Both of them have been crapped on by WWE.