I'm not sure where the more difficult came from but I would say it may be a bit different in areas. Previous exams tended contain a bit of "what's on this menu" or "where do you go to...". The new exam is more concept in nature. "If you wanted to do xyz, how would you accomplish this?" type of thing.
I would still prep but I think if you have a base level of the concepts behind what Marketo does (engagements campaigns, segmentation, different types of programs, reporting, etc.), it should be fine.
If anything, it may be easier because you do not need to know what's on a menu in an area you never or rarely use.