The slightly more advanced technological look of Enterprise is more akin to the New Earth timeline as opposed to the original.
I am aware of the fact that it was intended to be part of the Prime canon, but frankly it so terribly conveys continuity with those series that to me it makes more sense for it to be an alternate timeline.
It's reasonable to think that the events of First Contact created an alternate timeline that Enterprise and Star Trek 2009 take place in. Interference from the future could explain the more advanced looking technology in the series and the movies. I also refuse to believe the events of the episode "Regeneration" took place in the same timeline as later events in TNG.