Evening! Chris, to clarify the point, droppers are reasonably accurate for liquid reagents but when compared to a tablet there are chances for error either miss counting through distraction or drop variance, so between the two tablets are individually wrapped and sealed from the air until used, cheaper to ship and generally more reliable as a measured dose.
Roland, most testers require a reagent added to a sample, there are some strange versions out there, I bought a few, years back but they also require re calibration via some for of accurate test so I can't recommend them. Photometers are good because there is no colour matching to be done. You are quite correct with the cyanuric acid/free chlorine level being very important because of people reliance on multiaction tablets. Dip strips maybe ok for pH but the chlorine levels are only indications of chlorine presence rather than specific levels which we can use to diagnose problems. You cannot measure cyanuric acid with dip strips, you may get a colour reaction on the strip but it will be no where near the actual level determined via a turbidity test.
It's down to budget, as ever the devil is in the detail. Low cost looking units frequently ship with low amounts of test reagents, add the test reagents to the level of the other units and then get a comparison, which is why for the value version it has to be the ColorQ Pro7 at the moment as it tests for more and contains more reagents. The only real dowside with that unit is the test tubes (don't be frightened) are plastic and get scratched with use so need replacing as the scratches scatter the light beam used for testing. The tubes are cheap, I found some lab grade glass ones but at £75 for 3 i don't see many people buying them.
Other good testers are comparator types which are similar to what you have now but with a much better and more accurate range of colours which actually match what your testing. There is the titration type testers, very accurate too you count the tablets/drops until a colour change occurs but these are more CSI in my opinion but if you used to work in some laboratory the technique will be known to you.
The tester you have now is known as the OTO test and it only measure Total chlorine and not free chlorine, you need both as you are looking for a difference between the samples of 0- 0.5ppm.
I can ship the testers to France or the UK, just drop me a PM or email.