How accurate are motherboard temp sensor vs third party software sensor?

[Qianglong]

When I use the ASUS utility to check on my CPU temp at idle it shows 27C but if I use any other third party software such as CoreTemp or OCCTPT the temp is at least 8C to 10C higher than the ASUS utility.

I am wondering which is more accurate or should I just take the two temp and divide them by two lol...