The tropic Marin hydrometer is and has been my first choice, since I’ve been searching for a US vendor to have that in stock even before purchased everything for my build... Impossible.
Also forgive me for the two part response, but the only viable vendor RIGHT NOW is eBay (German vendor), where your given the option to purchase it with a graduated cylinder which I think is awesome +saves you a trip to the odd science website + ensures your not experimenting with other containers, BUT shipping is 3+ weeks which is excessive for my situation.I personally use the Hanna HI96822 digital refractometer.
It is simple and easy to calibrate and has been very consistent. I do warm it up with my hand to 78 degrees prior to calibrating or measuring to ensure that the sample is as accurate as possible.
There is deviation if there is a large temperature difference. This is true with all salinity measuring tools. They all claim to have temperature compensation built in, but beyond a few degrees they start to lose accuracy.
I would not recommend the hand held pen style Hanna salinity tester.
It drifts a lot and requires constant recalibration. You also have to use their 35ppt solution to calibrate it which is a consumable item (I have tried to use others and it never "recognizes" them). People seem to love them, but I question how they feel about them after long term use. Works great as a thermometer though.
The "Gold Standard" for me is the Tropic Marin High Precision Hydrometer. Noting to calibrate and it just works every time; just at the cost of ease of use.
And the "I'm not just sharing bogus information just to hear myself talk" photo... One is far better than the other.