Neither are any good. Unreliable.

You'll want a water ph tester. (ph pen)
Something like this:
Discount Hydroponics - Waterproof Testing Pens
It's the one I use, and works great.
If getting the calibrating solution for it too, get the 4.o1 ph stuff. Can also use this liquid to store the pen.
It's easier to use than it sounds, and worth every penny.

If this is out-of-reach for now, I used a freshwater aquarium ph kit for years. ($6.oo) Keeps you in the ballpark, but not very reliable for testing run-off ph.