I believe that Hagen test kit is a 3 part solution where you drop shake and count how many drops until it changes color, either way, how "good" it is is really subjective.. do you need to know your calcium down to 1 decimal place? Or would you be happy for a range of +/- 20 ppm? ie you read 420 calcium.. so you have anywhere between 400 and 440. If you can say to yourself "this is accurate enough" then by all means get the cheaper kit, you'll be wasting money on a high end kit.
of course if you're measuring something like pH then you might want a little more accuracy. But ask yourself what your needs are, then buy accordingly.