Civilian GPS units usually have a very small factor of error , this is usually only a few meters in Lat, long and elevation.the one in pic is within this "few meter" range.My magellan does same thing,it will even give a different elevation for same peak on different days...not by much though!
I would trust the national geodetic survey's reading of 10,064'.If they can determine that Everest grows about 1/4" a year, I think they can tell within a few inches for Baldy.
Also, the Garmin website says that the elevation accuracy may be off by as much as +/- 400' depending on positions of satelites at time of reading.....wow!
Who knows for sure the true elevations? It is interesting, though, that the latest elevation for Mt. Whitney is 14,505 ft.--making it the only peak in the lower '48 over 14,500 ft. Almost more note-worthy is Mt. Williamson's new elevation listing--14,403 feet; a gain of over 28 feet! Do you suppose Mt. Barnard is over 14,000 feet again?
"After the first glass, you see things as you wish they were. After the second, you see things as they are not. Finally, you see things as they really are, which is the most horrible thing in the world."
--Oscar Wilde on Absinthe