Trident for alk, Ca and Mg. Given the frequency, makes much more sense to automate.
Hanna all the way for others: alk, salinity, nitrate, phosphate, and copper when you need it.
The LR nitrate is a PITA and the Ca is finicky at best.
pH is part of Apex, so I don't care much about measuring that.
It would also be good to keep a back up salinity, Milwaukee digital is a good option.
I don't trust the color scales on the others, as I can't distinguish the colors well enough to get a good value. Plus, the ease of seeing a number makes it worth the while.
Like others said, testing is critical. I wouldn't limit yourself to just the sponsors here...
Spend your money wisely when it comes to testing. It will make a world of difference!