Yes, the i7 is one heck of a chip, it also carries one hell of a premium price tag as well with needing to have a new MB, expensive ram, etc. HT as you said, only can show any gain if the core's are not under full load. Under full load performance may actually slightly decrease.
i7 is definitely far ahead. Nothing else to say about that.
As for multimedia, I'm still suspicious of the compiler technology; architecturally K10's SSE support looks really good on paper. It seems to me that we just haven't seen code that was generated properly to take full advantage of it. And HT really doesn't buy anything if you can keep your active cores sufficiently fed that they have fewer stalls.