krysh:
A lot of this comes down to how loud the environment you will be playing the guitar in is. The soundboard transducers can sound very good, but are susceptable to feedback if the ambient volume gets high. I know high is open to interpretation, but anything over a small coffeehouse gig, or background music in a restaurant gets to the point of triggering feedback, as would playing in a band with a bass, or drums. The same is pretty much true for a microphone, with the added complexity of not having the freedom to move around a lot, as the microphone's sensitivity pattern must also be considered.
In louder situations, or more of a plug in and go situations, USTs and magnetic sound hole pickups are more feedback resistant. It is my opinion that magnetic sound hole pickups make your guitar sound like an electric guitar, which is OK if you just want to get the song across to the audience, and do not play with a lot of nuance, as this pickup pretty much disregards any body resonances. The UST can be better, especially with the high headroom pre-amps, one of which is the DTAR. I have heard two DTAR Timberline installations, and one Wavelength installation, and was quite impressed with both pickups (the Timberline actually seems to pickup body resonances more). Note that the Timberline does degrade the acoustic sound of the guitar more than the Wavelength.
The basic installations are pretty close to standard UST installs, with DTAR placing a high emphasis on complete contact between the transducer and the saddle/bridge (curved bottom bridge slot and curved bottom saddle for the Timberline, as flat a bridge slot and saddle bottom for the Wavelength. Both pickups are noticeably less prone to quack than any other UST I have ever heard.
Another alternative is to use one of the processor boxes that are out there: the Fishman Aura and the DTAR Mama Bear. Both can really produce very good acoustic sounds, but the Aura needs to have a model to work really well (there is an ever growing list of models on the Fishman Aura website). Bot boxes work with either UST transducers, or with magnetic pickups.
Again, as a personal opinion and experience, I have never found internal condenser microphones used by themselves, to sound very good. I find them to be very boomy, and extremely susceptible to feedback. While I am sure that there are some good internal condenser microphone installations (mostly in conjunction with other pickups), philosophically, I don't like the entire concept. Its sort of like listening to a guitar by sticking your head inside the soundhole. You hear the guitar, yes, but you also end up hearing a lot of the internal soundwaves bouncing around inside the guitar.
All in all, I think Guild did really well to pick DTAR as their pickup vendor.
Kostas