Many of the folks here including me recommend the liquid test as they seem to be much more accurate. I started with strips and the readings were far different than that of the pet store I was going to who uses the liquid tests. Both Butterfly and Gunnie recommended that I get an Aquarium Pharmaceuticals Freshwater Master Test Kit. I found it onpetsmart for half the price that I'd seen in stores.
I like the liquid tests too. Using them kinda makes you feel like a scientist.
I noticed that products online at petsmart and petco were cheaper too. I'm not sure why that is - maybe the local stores are franchises and individual store owners can mark up the prices locally and/or to pass the shipping costs on to the customer???