They don't sound at all like an acoustic guitar, though, they sound like an electric hybrid. I like that sound myself, but it may be a bit too electric for some people.
As with the DynG sounboard transducer (that needs ample highs added), key with magnetic pickups is EQ-ing. Those need a lot of clean up in the mids. Then you can get pretty convincing results. Not quite truly acoustic but more musical than most undersaddle piezos, especially for fingerstyle (less so for strumming).
Not the cleanest by all means, but extra sweet ad musical (after serious EQ-ing) is the DiMarzio DP139 IMOAE. I think it's discontinued, though. It has adjustable pole pieces (which is important for me) and it's easy to install and remove, without screws.
For piezos, check out K&K's Pure Western Mini. It's passive (but not thin sounding if used properly) and resides on the bridgeplate, inside the guitar. Somewhat more prone to feedback, but more natural sounding to my ears than undersaddle piezos (and even coaxial cable, electret film and whatever can be buried in there). The latter do improve with higher voltage preamps, but they'll remain more spikey. Well, unless digital tricks are implemented. But I think I'll stop here.