As jefe said, both processors will do the job well for plain old programming. (I'm a longtime .NET developer myself, using VS2008 and VS2010 currently.) Even an i5-750 would do fine. I looked at the differences between the i7-860/870 and the i7-920/930 and concluded that either way, great system, but the i7-860 edges out the i7-9x0 in general performance, energy efficiency, and motherboard selection (although I imagine that's an area that could change pretty fast).
In terms of anything more than an i7-870, IMHO save your money. You can easily overclock an i7-860/870 (they're actually the same price now, so might as well get the i7-870) to 3.6 GHz or higher (buy a cooler) -- same goes for an i7-930. Instead of blowing extra bucks on a marginally faster CPU, buy an SSD. After my RAID-10 array bit the dust, I threw in a Kingston 128 GB boot SSD ($250 on NewEgg) and it just runs fabulous. Smokes even my superfast ex-RAID-10 array.