That's not entirely fair to Viz, of course. When a manga has made-up vocabulary it's always easier to read in Japanese because the kanji alone tells you what the thing means. No need even to sound the Japanese out. Yeah, so that's your cutting-spirit-blade, fine, (unless of course ceci n'est pas un cutting-spirit-blade) and eventually you register 'oh *that's* how zanpakuto is written.' A transliterated Japanese term requires explanation and still doesn't stick, because hell, it's just a random assortment of sounds. That goes double for the names, which are more important than various attacks.
Equally, reading shounen dialogue in Japanese is automatic because it's stock shounen dialogue that we've all read a million times before. Thus one can skim. Unless you've read translated shounen dialogue a million times before, you have to actually /read/ the English and it makes no sense because, hell, it's translated Japanese dialogue that doesn't make sense in English. Like reading someone saying 'I beg you' in a translation from the French, which is an eye-stopper, where je vous en prie would barely register in the original.
Also the artwork is so much better in the original. The loss of detail in translations is one of those things I never hear complaints about, and should.