Look for links to reviews on the forum here, and there are youtube videos on most of the models:
The Extech MM570 is basically the same as the Brymen BM859:
The Amprobe AM160 is a recased version of the BM859:
The difference between the BM857s and BM859s is less rated accuracy and no temperature measurement.
The BM867 was reviewed in detail by Martin too:
Dave did a short overview of some Brymens:
The BM829s and BM525s have not been on youtube yet, but will be soon. I will be doing detailed reviews of the BM257, BM525s, BM829s, BM869s, BM22s, BM27s and a clamp meter BM089.
The short story is that the BM857s is the equivalent of a BM867s but without dual display and with a different case. The basic accuracy is 0.03% against the BM869s 0.02% and CATIII/1000V instead. These have 50,000/500,000 count and are very fast, safe, and very well built.
The BM829s and BM525s share the same case as the BM86Xs but have only 10,000 count and 0.08% accuracy. What you get instead on these is an auto-check feature which is a low impedance AC/DC, Ohms, and continuity test in one setting. The BM829s adds a non-contact voltage detector, and instead of the NCV the BM525s adds an 80,000 measurement logging internal recorder which can measure up to 20 times per second. To get the real benefit of the recorder you need a PC cable for around $50.
The BM257s is a really great all round handy meter that is much smaller than the others. It is basically a mini BM829s with 0.2% accuracy and 6,000 counts, and is rated CATIII/600V instead of CATIV1000V, EDIT and does not do TRMS AC+DC but only AC. It is one of my favorite meters because of its size and utility for on the go. It is probably more than most hobbyists would need and can be purchased with the PC cable for less than $200 shipped.
My recommendation for most people would be to get a BM257s or a BM829s and if you want the measurement recording capability then the BM525s. Only get a BM857s if you don't care to have temperature and don't think you will miss the dual display of the BM829s or BM525s. 50,000 counts is only an advantage sometimes and 500,000 counts very rarely. The number of counts exceed the accuracy so they only let you see small changes rather than let you see real absolute values.
Of course the BM869s is really nice but I think that for the same cost as just a BM869s, a BM525s with a PC cable is much more useful with its logging capabilities.
If you do buy any of the Brymens, get the magnetic hanger too, it is handy.