Its just price. You can generally now buy an optiplex i7-6700 for 599 on ebay, with 3 year warranty. Its better than the inspiron.@fenderman. thanks for respond. how come you didn't recommend Skylake CPU? is there any drawback beside pricing? I am thinking about building a skylake i7 6700K since I already have some case and psu and ssd alaready. I am plan to run at least 16 Hik 4MP cameras. Today Dell has Skylake i7 for $580 http://dealnews.com/Dell-Inspiron-Skylake-Core-i7-Quad-3.4-GHz-PC-for-579-free-shipping/1725992.html. and i5 haswell for $350 http://dealnews.com/Dell-Vostro-Haswell-Core-i5-Quad-3.2-GHz-PC-for-349-free-shipping/1725956.html. For my application, which one should I get?