Pel
In recent years nobody has made side by side comparison of kits and meters for accuracy. So, it is hard to say who's is more accurate. Salifert has been the leader in this hobby, especially as their kits are direct at seawater. I say seawater, as most kits in this hobby are really FW kits/ meters and seawater skews the readings of many FW kits/ meters, as the salt in seawater cause reading errors. The Red Sea kit is a very well put together kit but sill suffers from seawater interference. It is not all measurements that do this. For us it is mostly the Alk that is skewed but not in the Salifert Alk kit, as it is set to seawater. If I was picking for you it would be Red Sea for all, but the Salifert for Alk and the Hanna meter for Phosphate. Lastly, one of the most difficult things to measure and get it right is Alk. And when we say Red Sea, we mean the Red Sea Pro, not the older RS which are horrid.