Ph meters don't really last no matter what brand, unless you get lucky. Be sure to store them in RO water or 7.0 solution, regardless if it claims to store it in 4.0
Anyway.
I haven't tried Milwaukee ph600aq
I do own the Milwaukee (martini instraments) waterproof ph55. It is super fast and accurate, plus gives temp, but only in C. Why can't I change it to F? It worked great, never really needing calibrating, until one day it read all wacky. Would not galibrate to 4.0, gave errors. I bought new batters, still wouldn't calibrate. I let it sit in 7.0 solution for a while, then tried calibrating it again the other day. It's working like a champ again, but who knows for how long. I got about 5 months out of it before it went wonky. Only a few days since it fixed itself.
I bought a Oakton eco testr ph1. It worked for a month. Much slower than the Milwaukee. I'm hoping it just needs batteries. It will not read correctly and will not longer calibrate to 7.0 or 4.0. It is a one point calibration.
I own a hanna tds meter, beer style one. It has worked accuractly for like a year. No complaints, but I never tried a hanna ph meter. Don't want to because I only hear bad things about how long they last.
I will try a ph600aq and see how long it last. Heck, if it last 6 months to a year, that is worth it I guess.