been through most of the brands when i was working on tour.
started years ago with GHS. i liked that they were from michigan, support the home state, etc.
too bright to the point of brash when first installed, get dead and sound like crap very quickly, and i had a high failure rate with them.
d'addario sounds pretty good, but they also get dull quickly, and i also noticed a somewhat high failure rate.
don't have enough experience with dean markleys to say one way or another.
ernie balls are the best all-around for my tastes (rock, blues, country, jazz). they sound good to start, they seem to last the longest and don't break more than normal, and they're easy to find about anywhere you go. i like a 10-48 or 50 on my electrics.
i've tried SIT's, snake oil (boutique high end strings), gibson, etc...
i've been liking a set of john pearce strings on my acoustic, although the gauge i tried is a little too heavy.