It sounds logical to think that a quad core processor is better than a dual core processor. It all depends on what you want to do with your computer. Many dual core processors are faster than quad core processors. Some of this has more to do with marketing than science. Sometime in the 2005 to 2008 time frame chip makers started making quad core processors out of what had been a dual core processor. They gave the dual core chip 4 threads instead of 2 threads. Sure it was now a quad core processor, but they were not able to perform real quad core processes.
For two decades most people thought that the gigahertz number on a chip determined the speed of the processor. Gigahertz speed is the number of cycles a processor can run per second. If you compare an Intel i5 processor with a 3.1 gigahertz speed with an Intel i5 with a 3.6 gigahertz speed, the 3.6 would operate at a faster speed. You cannot compare an Intel i7 processor with a 2.9 Gigahertz number with an Intel i5 processor with a 3.3 gigahertz number and determine that the i5 is faster. The i7 is a different chip with factors that override the gigahertz speed.
Moving forward to the processors available today and things get even more complicated. I could spend all day trying to explain all the new technology, but we would both get bored. Intel or AMD? If you are building or buying a gaming computer most people choose an AMD processor. They just seem to squeeze more speed out of a processor. The AMD speed does come with some baggage. Intel chips are more reliable, and the speed difference to the average user is negligible.
With the drop in price for the solid state hard drives, processor speed is not as important as it was in the past. On average a solid state hard drive is three to five times as fast as a mechanical hard drive. They have no moving parts, and with flash technology they are much faster and consume less power. Confused yet? If I were looking for a computer that would be fast enough for just about anything that the average user would need to do now or in the future, it would be configured as the example below.
The processor, any Intel i3 or i5 processor, 8 Gigabytes of ram and a solid state hard drive. Forget about the generation of the processor because that is just marketing. Remember we are talking about real world usage. We don’t care if one is 2 seconds faster than the other. If you are looking at a desktop computer you may want to buy a one or two gigabyte graphics card. These cost from $50 to whatever you want to spend. Unless you are a gamer a one gigabyte graphics card will meet your needs. If you are buying a laptop, you are going to be dealing with integrated graphics ( the graphics is shared with the processor). Some laptops do have an on-board card but they are expensive and not needed by most people. You want the laptop processor to be at least an HD 4000 series.
This information is based on my many years in the computer repair business. There are many different opinions out there. This information is just a simple guide for someone looking for a good all around computer.