I play in all the brackets, for various reasons.
19 because of higher availability of organized play, lack of crippling on rogues leads to better teamwork, etc.
29 because it also has a high number of twinks, and while synergy between classes is important its not all encompassing; a lot of options open up that just arent viable at 19 (balance droods, for example. Healers get 1.5 second casts.)
39 because of balance. Its still the most balanced bracket, where any class can feasibly defeat another. With the relatively recent hp nerfs, burst classes do stand out a good bit from the pack, however.
49 - Burst is fun, but healing through it is better. The high damage:hp ratio keeps you on your toes.
Havent liked 59s since DKS came out, but they do ensure you at least have someone kinda well geared, even if they dont know how to play, on your team. 60 AV tends to be a DK fest, upgrading guards etc is pointless cause a noob dk can tear through them so fast.
69 because DKs have to work to stay competitive with there gear. A lower number of twinks:normals means higher impact from each twink. Ret pallies are OP, but so satisfying to kill. Every class can be well represented by a twink, balance here is amazing. A little burst heavy. 70 AV can be very satisfying, and seems to have the most even win:loss ratio of any bracket.
79. I've never liked end-game pvp since BC + resil came out, but the 79 bracket's not bad. With the very easily attained crafted resil sets, everyone is on a relatively even footing, which is a good thing. This is the first bracket where you can reliably swap from a *resil* based set to an all out dps/heals set.