I find the Red Sea Pro kits WAY easier to use. The instruction cards are so simple, the hand held titrator for titration tests and the colour wheel for other tests are so easy to use, the test kits have really nice hard cases, the droppers are really easy to use and everything just feels quality.
BUT the colour changes on the titration kits are crap. Calcium and Magnesium pro kits are ok but still not as quick of a change as I would like, there is sometimes a bit where you wonder as it isn't red anymore but still not quite blue. But the Alk pro test kit the worst. I have used 3 different reagent solutions and it is just horrible when it comes to the colour change. It is almost impossible to determine a distinct end point, the colour just changes very slowly over the course of 5 or so drops - not good enough IMO.
The Nitrate and Phosphate kits are ok, but you have to wait 9 minutes for the Nitrate kit and 6 minutes for the Phosphate kit.
I have just switched to Salifert and without a doubt there are things I miss about the red sea kit (nice instruction cards, titrator and colour wheel). But the colour changes on Alk, Ca & Mag are all very clear which is what is really important with test kits. And the Nitrate kit only needs to wait for 3 minutes and the Phosphate kit doesn't need to wait at all which just makes testing a lot nicer.
Overall I would recommend Salifert over Red Sea for sure
