Reef keepers often perceive the LaMotte test kits to be "better" than Salifert because LaMotte provides a glass test vial and a plastic case, while Salifert includes a plastic test vial and comes in cardboard.
Actually, the reverse is true; the crystal polycarbonate test vial used by Salifert is a modern labor
atory standard, while the green glass vial provided by LaMotte is unacceptable for laboratory use (green here refers to a grade or quality of glass, not to a color).
Crystal polycarbonate as used by Salifert is chemically inert. About it's only real fault is that it can get scratched up over time with use; crystal polycarbonate labware is generally considered disposable.
In contrast, ordinary green glass like that provided by LaMotte leeches alkali compounds like crazy because of the way it's manufactured, which can materially alter the pH of the test sample. This may or may not significantly affect the outcome of the test depending on the test protocol used and what's being tested for, but it's amazing how much alkali comes out of cheap glass, and for how long.
Glass like that from the LaMotte kit really needs to be pickled in acid for a long time (days) before it can be considered lab-safe. To be really lab-safe with glass, you need at least a good grade of borosilicate glass, like Type-1 Class B borosilicate glass or above. Truly great glass labware, something like Wheaton-33 low extractable borosilicate glass, is prized by scientists for the most precise testing work and costs big bucks. Since you won't get good lab glass like this in any throw-away test kit, look for good-quality plastic vials like Salifert's.
Even the best glass, and plastic too, needs to be washed after every use with acid at least as strong as 5% acetic (white vinegar), and dilute hydrochloric acid is even better. Many things for which reef keepers test, especially orthophosphates, stick to glass and plastic so well they can't be washed away with any amount of plain water. How many reefers acid wash their test-kit vials between tests? Not many, I'd bet.
While I'm picking on LaMotte here, I can't help but mention their Calcium test kit. The salt water instructions call for the user to measure out exactly 1.0 milliliter of tank water to be tested. To accurately measure 1.0 ml requires something like a 10 ml Class A PFTE burette, marked in .05 ml increments. But amazingly, LaMotte provides only a plastic eyedropper, and one that holds only 0.5 ml at that. Just the error that comes from using this eye-dropper to measure the all-important water sample can completely destroy any hope of really accurate testing of such a tiny amount. For the user of average skill, this kit presents some real problems, and only an experienced and very careful user can get decent results from this kit.
With all due apologies to the LaMotte fans on the board, I can't help but suspect that at least part of the reputation that LaMotte test kits enjoy is due to their high pricing, and their packaging - although exactly what the sturdy blue plastic box has to do with the supposed accuracy of the test kit inside frankly escapes me.