Yeah I agree it would be a good idea, even just on the basis we will get to see how all of the current generation's lives play in the how ever many years that pass.
It really depends I usually prefer to watch anime in my own language eg Dub although I have no problem watching sub but one thing I can't do is change from Dub to Sub half way through a series I get really put off my it. Also it depends on the series them selves some are better dubbed some are not
I would also like to know as it looks extremely good. But back on to the original question yes they are all worth watching basically they are extended episode but that is not a bad thing in this case
Hard one this, well Kenpachi got the greater physical strength of the two and is a skilled sword fighter but Byakuya is faster and has Bankai so I don't know but I'm leaning toward Kenpachi
A lot of it is not original but I enjoy watching it and have recently started watching again from the beginning (due to the slow release of episodes) and it's still great second time through