Had to vote for the X2. Poll just asked which would I go for, with no circumstances named. If I could afford either right NOW, then money isnt really an issue anyways, so why not get the better performing of the two? I dont think many would defy logic and contend the 8xx actually outperforms the X2, just that its cheaper. I dont really have a brand preference, if performance/$+heat and noise ratio were close I would have no problem getting intel, Im a huge fan of the PM for mobiles and my GF just got one on my reccomendation.
Also since no circumstances were given, I just took my own for when I do go dual core. I (and many, if not a majority) already run a 939 setup, 3200, Neo2, 1GB ram, 9800xt. I plan to get the X2 3800 when released (few months or less supposedly), supposedly at $345, and I'll want an extra gig of ram also so an extra $75 (value only for me after reading Zebo's thread), $420 running total. -150 cpu (ebay) = $270 total upgrade.
If I went intel, lets say $200 for the cpu (same few months assuming generous price drop to be fair), then $125 for i945 MB comparable to neo2 (generous I think), $160 for 6600gt pci-e (tricky forced video upgrade, comparable to 9800xt but lose 128mb ram), then $175 for 2gb value ram, new water blocks for cpu and vid card $100, running total=$760. -80 MB, -150 CPU, -60 RAM, - 200 Video (ebay) = $270 total upgrade + alot of sh!t that I would rather not deal with.
For me I think the extra hassle involved with switching to PD alone is worth going X2, plus I think it will perform better and save me money on electricity bills for the extra power draw, and extra time the AC will run to keep my room cool. The reason I laid all this out is because I have a suspicion that most of the ppl here who could use a dual core cpu today already have a 939 setup today, ive had mine for a year and a half already and M2 wont be out for another year, sometime after (hopefully when DX10 or whatever cards become available) that I'll change motherboards, and pci-e VCs and DDR2 should be cheaper than agp and ddr1, 2 1/2 years dont seem bad to keep a motherboard to me.
What will I miss out on? A higher latency memory tech? A new bus protocol that doesnt really improve VC performance and no add-in cards for 1x will be available til I go that way anyways? SATA II? SM3.0? all hardly gotta have-its to me right NOW.