There isn’t really a straight-forward answer to this, despite what most will tell you. It largely depends on what you will use the pc for. If you are only going to game on it, a cpu is less important than a good graphics card and fast RAM – an Intel Core i3 or AMD A-series apu will be more than enough for most games. If you want to run CloD at its best your choice of graphics card will do it, but I would recommend a faster cpu than these.
I have both in my household; mine (in my sig) and my son’s Core i5 2500k in a Gigabyte Z68 mobo, so I can easily run comparative tests. The main difference between the two is that the AMD cpu needs to be overclocked to provide decent performance, while the Intel does not. You also do not get the same increase in gaming performance by overclocking the Intel cpu, as it’s not much of a ‘bottle-neck’ to start with. Currently mine runs games slightly faster than my son’s, but mine is at 4.10GHz and his is at default. Both have ‘turbo’ enabled, which results in mine running CloD at 4.30GHz and his varying between 3.50 and 3.70GHz. There are many articles on the ‘net demonstrating that these two have almost identical performance when both are overclocked to 4.50GHz.
If you’re not much of a geek and would prefer to leave your cpu at default, I would recommend an Intel Core i5 3570k in a Z77 chipset mainboard – this will give you the maximum ‘bang for your buck’ without any need to fiddle with settings. It will also allow you to easily overclock it in future should the need/desire arise, being that the cpu has an unlocked multiplier. Spending (a great deal) more money for a higher-end Intel cpu/system will not result in any useful increase in gaming performance – in fact, in some cases, you may get less
If you would like to go the AMD route, PM me and I can offer some useful advice.