6s vs. 4s?

[georgec]

Recently there have been some guys from Kentucky and Georgia coming to race with us at our local track (great bunch of guys) and all of them have ran 6s with 1400kv motors. A couple of them let me drive their buggies (MBX6) and they did seem to be noticeably smother than my 4s/2000kv setup and their motors all ran 5 to 8 degrees cooler. They didn't seem to be any faster than my setup just smother. All this has made me second guess my setup. Could it be that running higher voltage with a lower kv motors is that much more efficient than lower voltage with higher kv motors??? The overall cost is about the same because the batteries they were running were only 3300mAh as opposed to my 5000mAh and getting the same run time. As for motors they all ran the Tekin 1400kv, witch I don't know much about other than the price isn't bad. The funny thing is all but one ran the MMM esc and only one ran the RX8 esc.
Any input on this