To choose processor first thing I decided is that I want to do with the computer in my case what I want is:
Virtualize multiple operating systems simultaneously, have a server, multimedia and data in continuous operation, run CAD programs and finite element.
In your case you should consider what you want to do with your computer.
Depending on my needs I think my processor should have power to throw multiple operating systems and programs and calculation cad, must consume little electricity because I will have always on, must incorporate virtualization technologies, as the media server does not need much power if you do not care.
With this data I will any online store to see what products sell me always try to look at least three stores to compare prices and products.
In my case I am left with two processors with the characteristics I want one of AMD's FX Series FX-8320 3.5Ghz 8X € 129 and one of Intel's Core i5-3570K 3.4Ghz € 189 I choose these two for several reasons:
Meet the technical specifications required of power and Virtualization.
The price is affordable to my pocket , although intel is me doing pretty budget.
Prices for these are more powerful long shot and power are no longer in relation to the price.
You can choose as many processors as you want.
Once you have chosen the processors will http://www.tomshardware.com/charts and within any framework charts processors processors that interest me and say that compare. Tomshardware performed comparative potential of the components in the matched conditions and more with a lot of different tools.
Getting the following result Tom’s Hardware – Benchmark  Abbyy Finereader
Comparing the (the mas en tu case) processors can analyze the power difference there is between the two. In almost all cases, the intel is more potent, as expected.
The next one price point AMD vs Intel € 129 € 189.
The last thing to discuss is the power consumption on Intel specifications consume 77 Watts and AMD 125 Watts is the difference 48 Watts.
According to this ad http://es.calcuworld.com/calculadoras-de-ahorro/calculadora-de-consumo-electrico/ 48W consumption throughout the month is 28.8 kw / h month representing a monthly savings of € 4.34 , also looking at google find this page http://www.anandtech.com/show/6396/the-vishera-review-amd-fx8350-fx8320-fx6300-and-fx4300-tested/6 comparing the consumption of the two processors. With what I have very clear that AMD uses a lot more electricity than Intel at worst producing annual savings of 10-20 may reach € 52 € if you were at full power all day . If I give a little cane to computer savings will be much greater.
What with me and it's clear that I'm buying the Core i5-3570K 3.4Ghz because it is more powerful and cheaper long term .
Your purchases as a processor?