Can anybody give any direction/guidance in the choice of choosing a single coil or humbucking soundhole pickup for an acoustic guitar...!
The typical response regarding the difference between the two goes something like:
Humbuckers are "warm", where single coils are "thin".
Single coils are "chime-y", where humbuckers are "thick".
The Neo-D is available as both a single coil (lower price) and a humbucker (costs more). Both Dean Markley and Seymour-Duncan offer similar choices with their ProMag and Woody pickups, respectively. The more expensive Fishman Rare Earth and Blackstack are humbuckers. As are the Sunrise and Baggs M1 and M80.
Frankly, the humbucker better respects acoustic "properties", where the single coil is, well, downright "reedy" sounding. The Neo-D, by Fishman's own admission, is a low-cost solution. There is nothing wrong with either the pickup or with pursuing a low-cost solution. But back up just a few feet for an overview:
If you want to get down and dirty with your acoustic, and already have an electric pedalboard, a magnetic soundhole-mounted pickup will get you there. The more expensive models can
also get surprisingly close to a "natural" sounding acoustic guitar, especially when blended with another technology (piezo or mic). Single coil pickups are more susceptible to "hum" than are humbuckers (hence the name), but cost less. And they are super-simple to install.
If you are trying to squeeze out a bit more "natural" sound out of your guitar, and if you are willing to invest just a bit more money, a SoundBoard Transducer may be more pleasing to your ears. I believe that, for $99 (and some installation effort), the K&K Pure 12 string SBT that you identified will, when installed correctly, be a very satisfying solution. If you want to improve even more upon the sound then, down the road, you can invest in an outboard acoustic guitar preamp.