I can tell you that the Hanna out performs the extech hands down , my first ph meter was the extech and at first it worked okay , then it started to wander in ph as I was making the cheese and would have to do an emergency cleaning ( in panic mode as it always did this near target ph) finally I gave up on it and splurged for the Hanna , best money I ever spent .
Any one making cheese more than likely has more money tied up in molds and cultures than the cost of the Hanna halo probe @$200 or so , it should last about 8 to 10 years for a hobbyist before wandering ph too much so some where around $20 per yer. As I said money well spent .
Gregore