Here, This will add to the confusion. I bought a split off acreage from a farmstead. The surveyor GPS'd all the waypoints ( 15 or more ) put in posts and ribbons. Weeks later a Geocache friend came by with his hopped up GPS and put in all of the coordinates. All but the 1st one were wrong by a 3-5' margin. So, Who's GPS is accurate. This guy does Geocache all over the world. That being said, Another surveyor I talked to about another property I own told me that their unwritten rule is whomever calls the surveyor to come out gets the benefit of the doubt on property lines. Nuts..
No confusion here; the Surveyor pays for a subcription which ties his unit into known points to provide sub meter accuracy... depending on what he has, he makes corrections in the office and has to go out afterward to correct his points. .
The other things that a surveyor has is a license, which he can lose if he consistently does half a**ed work; insurance if he does mess up; and the ability to testify in a court of law if his work ever came into question.
You can trust your friend if you want, but I will believe the word of the guy who has studied and made a career working as a surveyor.
My hand held Garmin gets me very close, and often seems to be right on; but that's just because it isn't as accurate as the survey grade unit.