Just my .02, but an electric guitar sounds and feels and plays and looks like an electric, and an acoustic guitar sounds and feels and plays and looks like an acoustic.
MANY have tried to incorporate the two...Line 6, Parker Fly, etc...but to the purist, it just ain't happenin'!!!
Like many here, I've been playing electric and acoustic guitars since the 70's, and I have tried just about every type of way to amplify an acoustic guitar there is.
Having said that, nothing sounds better than a microphone or two properly placed in front of a great sounding guitar and mixed into a professional sound board in a studio with a competent engineer at the helm. HOWEVER, that's just not practical in a LIVE situation for a myriad (plethora?) of reasons.
So...for live performances, especially in a band situation, we have to try to find ways to amplify our acoustic guitars.
In MY experience, soundhole pickups make a fine acoustic guitar sound somewhat "electric"....great for picking up the stings, but not so good at body resonance and that full acoustic guitar luscious-ness. And it's hard to balance the volume, string-to-string (the high E and B, especially), even with adjustable pole-piece models, unless you put electric strings on your acoustic and then it doesn't sound so good acoustically. And it really doesn't let your guitar sing!
UST's generally have a somewhat brittle "quack-y" sound, especially when played aggressively, and need a LOT of fiddling with EQ and levels to sound decent. On-board pre-amps help somewhat, but they chop a hole in the side of your guitar, and still not ideal! I WILL say that the DTAR Multi-source system really sounds great, UST, but with a higher voltage for more headroom before quack, and a little onboard mic you can blend in, and with the soundhole controls you don't have to chop a hole in your guitar...but you still need to load batteries into your guitar. And you still lack a little warmth...and be careful dialing in the mic...that puppy will HOWL!
Putting a mic specifically designed for acoustic guitar amplification inside your guitar CAN sound OK, depending on the quality of the mic and it's placement...but feedback is the main problem!
L.R. Baggs I-Beams and their little Lyric mic-thing CAN sound great, especially with their foot pedal pre-amp, depending on the guitar, but placement is crucial and tedious, yet it can yield great results. However, feedback can be an issue.
The best system I've ever used, and still use, is the old-fashioned passive K&K Pure Mini with volume control, with the Pure Preamp. Its a multi-point (3) soundboard/ bridgeplate transducer. Makes your acoustic guitar sound like your acoustic guitar...only amplified. Feedback can still happen, but you can do a LOT to minimize feedback without sacrificing tone. If you have a great sounding guitar, it'll make it sing! If you have a crappy guitar, it'll just make your crappy guitar louder! LOL!