I suggest just looking into post processing of any ouput filetypes you might be able to generate aside from gpx or nmea. I looked into it for gpx files long ago. Not enough information in gpx/nmea file relating to the individual satellites signals. Fairly certain this is hardware/firmware level difference though, so seems fairly unlikely. Hard to find mention of it on here anymore, but ESRI used to stand for Environmental Sciences Research Institute... A Trimble is a professional tool with one very specific purpose... An iPhone is a gadget that you already had in your pocket..... And it has a GPS on it. Unless you turned off the cell/network "processing", your gpx locations would be based on a weighted average of trangulated location and satellite data.
Oh forgot.... You ever used point averaging? I remember thinking I was going to use that with a Garmin one time and live with crappier data. It would have taken a week to collect 20 locations to within a meter or two..... Skip.....
This link is possibly older, but same reasons apply.
poorgps