K&K Pure Mini (passive). Pure, natural sound (sounds like an acoustic guitar, not a bad Telecaster), no quack, no effin' battery to fart around with. As it's an under-bridgeplate pickup there's nothing goes under the saddle to interfere with the unplugged acoustic sound. I took the USTs (Fishman) out of all my guitars and replaced them with K&Ks.

You can add an outboard pre-amp if you wish (make sure the input impedance is a match - 1 megohm, not the 10 megohm required by, for instance, the Baggs Para-DI), K&K do a very good one to match the pickup.

K&K Pickups

Some will tell you they're prone to feedback - it's nonsense, all acoustic guitars are prone to feedback because they have sensitive, freely-vibrating bodies. Any decent sound-man can EQ it out. If you use a dedicated acoustic amp (mine's a Roland AC60) it should have a notch-filter to take out frequencies which are feeding back.

IMHO, YMMV, etc.