I can't comment on the Sennheisers but I have a pair of Creative's, although modified.
They have many good points, a only slightly subdued but nicely extended treble, terrific bass that goes really deep and a generally pleasant demeanour with a hint of warmth. The mid's seem slightly recessed but are very detailed.
Most of the compromise stems from thee cheap build ie. flimsy housing (it uses a quality driver) and it manifests itself in a sound that is more cuddly than it is attacking. - It was to cuddly for me but you may disagree.
Anyways, long story short, I dampend various bits and drilled the housing.
I wouldn't expect you or anyone to go that far but it is now a semi open headphone and to my ears vastly improved.