It's not an easy choice heh!
The Bloomfield 920 has been out longer than I realised and is a popular choice now, the boards that support have been fine tuned through BIOS revisions and you have a wealth of 3rd party heatsinks to choose from.
The Lynnfield 860 has been on sale like a week, alot of people scoff it or see it as a bad choice because the 920 can be had for less.
However I guess it depends if you wanna overclock or not and how you use your machine, the Lynnfield 860 is IMHO the most advanced mainstream processor in the world and has a number of benefits not found on ye old Bloomfield (joking heh, it's not that old!), like improved memory support, better Intel® Turbo Boost Technology, more power efficient etc
From early reviews the Lynnfield i860 seems to be overclocking very well too!
When comparing Bloomfield vs Lynnfield the former only really offers a few extras:
Tri-Channel instead of Dual Channel
QPI instead of DMI
Full x16/x16 PCI-E 2.0 Crossfire/SLI Support (vs 8x/8x)
Tri-Channel Memory looks good on paper, however from everything I've read it's not making hardly any difference in the Real world? I guess it depends how you use your PC
QPI has more bandwidth than DMI but again from what I've read the extra QPI bandwidth comes into its own when you have Multi Chip set-ups (i.e two separate processors both plugged into same board), also bare in mind some of this QPI bandwidth is being used up on the PCI-E 2.0 graphics (Lynnfield has built in PCI-E 2,0)
Lastly and I think the most important reason why some folks will say X58/Bloomfield is the prefered Gamers choice is if you plug in two really *monster* GPU's then you will get slightly better frame-rates on the X58 due to it offering the two full PCI-E x16 slots.
Personally, my own choice if buying today would be the 860, that's my own personal opinion and will not be shared by a gazillion die-hard Bloomfield owners heh!