I have noticed a distinct difference between my Trident and my Hanna checkers.  Sit back, I got some data for ya.
3-6 Set up Trident
3-9  dKh Hanna = 9.5    Trident = 10.9     delta 1.4
       CA   Hanna = 473   Trident = 540     delta 70
3-10  dKh Hanna = 9.4    Trident = 11.1     delta 1.7
       CA   Hanna = 543   Trident = 538       delta -5
3-17                      dKh Hanna = 9.8    Trident = 11.2     delta 1.4
Retest for belief     dKh Hanna = 9.5    Trident = 11.2     delta 1.7
                              CA   Hanna = 473   Trident = 455     delta -21
Retest for belief     CA Hanna = 538     Trident = 455     delta -83
3-31  dKh Hanna = 8.1    Trident = 8.2     delta 0.1
       CA   Hanna = 491   Trident = 431       delta -60
4-1 Replace Trident due to waste line not being connected
New Trident measures closer to Hanna
4-11   dKh Hanna = 9.4    Trident = 9.7     delta 0.3
       CA Hanna = 392 (did not write down Trident but noted closer delta)
4-28  dKh Hanna = 8.9    Trident = 8.97     delta 0.07
       CA   Hanna = 404   Trident = 571       delta 167
In short, the first Trident seemed to be off in dKh from my Hanna while the next unit tracks dKh very well, but trends high on CA by about 70-100 ppm.  The trends are pretty good and so I trust both about as far as I can throw them.  The Hanna being a little more because it's closer to a baseball than the Trident.
Ask me if you want to see my data book 
