What I am looking for in my Mac Pro is longevity.
I'm currently using the Mac Pro 1.1 I bought in 2006, the G5 PowerMac it replaced was about four years old (I think) and my brother in law used it for years more.
I generally buy the top model because I know I will keep it a long time- I generally use it for games, maintaining my iTunes library, light photo work (keen amateur who likes to play) lots of photos in Aperture, light programming.
My current MP is starting to feel a bit pushed. The fact ML isn't supported on it any more is a small but will be an increasingly important factor.
I did consider replacing it a couple of years ago and was shocked that the price of the top of the range (ie a dual processor) model had nearly doubled compared to my current one. But despite that it was the terrible, terrible experience at my local Apple store when I tried to buy that sent me home empty handed.
I've used an MBP for the last couple of years, with the MP relegated to home server duties, currently have an rMBP, but suddenly realised my rMBP isn't so much a desktop replacement as a desktop: it rarely leaves home. And compared to an MP is terribly noisy and I have so many cables and auxiliary devices (eg DVD burner, USB hub) cluttering up my desk I decided to bring back the MP into desktop service- until I can decide whether to replace it and if so with which MP.
Hence the question.
Oh and a quiet machine is important!
But all things being equal like you asked the 8 core is better. It has a better upgrade path, can hold more ram, has for the most part more processing power, and will have a better resale value.
The 2010 and 2012 are essentially the same system, with that being said what are your application needs?
If you do a lot of 3D work or video work the 8 core is better for you, if you do a lot of photoshop work a 4 core with a higher processor speed could be better for you needs.
But all things being equal like you asked the 8 core is better. It has a better upgrade path, can hold more ram, has for the most part more processing power, and will have a better resale value.
I can pop my processor board over to OWC and have them upgrade it so I can have dual 6-core processors if necessary and associated RAM upgrade.
The 2010 comes with 6 GB stock expandable to 64, the 2012 comes with 6 GB stock expandable to 32.
If you can afford the 8 core up front you have a much better and much cheaper upgrade path to a 12 core. All you need to do is pop in 2 new 6-core processors and recoup some of that cost by selling the 2 - 4-cores you pulled out.
So that upgrade will set you back about $2400. That's of course possible, but.... expensive. And I haven't heard about anyone doing it. You'll still be upgrading to old tech, and that $2400 is a severe write-off when/if a Sandy Bridge or Ivy Bridge based MP is released next year.
Everything else being equal (condition, Apple Care etc), which is the better machine? 8-core 2010 v 4-core 2012
Hate to be the stickler but the only 2010 8-core was 2.4GHz (Turbo 2.66GHz) and is Westmere-EP not Gulftown.The 2010 8-core is 2 quad-core 2.8 MHz Gulftown e5620 Xeons with 12 G of L3 cache; the 2012 is a single quad-core 3.2 MHz w3565 Xeon w 8 G of L3 cache. The 2010 comes with 6 GB stock expandable to 64, the 2012 comes with 6 GB stock expandable to 32. The 2010 has draft-n wifi while the 2012 has n wifi. Everything else is the same.