newer cores have better technology and ghz (frequency of core , aka how fast it can perform) with trobo boost to a higher clock speed(ofc you can oc to up to 5.0 with nitrogen cooling NOT RECOMMENDED). the higher the better, you will also see a cache as big as i7 4790k's 8M to E3's 64M(server cores) is a temporary storage for extreme fast transfers (way faster than sata and faster than pci-e speed) last but not least, GAMEs demand fewer core with high frequency in each core, where server demand more core with less frequence (so they can handle more client at the same time) Newer generation of i7 such as I7 6700k require a different motherboard that support DDR4 memory, which is the next generation of rams, if you want future upgrade, go with the ddr 4 with most updated core i cpu. i3 i5 i7 have dual core quad core octa core, i think the trend stop there, as you know i3 got lower frequence and cores than i5 then the same apply to i5 compare to i7.