I love my Aura Spectrum.
I have both: Fishman in the Tele, Graphtech in the SE245.
Fishman installation was easier, by far: just add a stereo jack to your guitar, and solder the hot and ground from the bridge to the jack. Has plenty of output for being entirely passive, even direct with no pre-amp, and I'm using the Aura as a pre-amp anyways.
Graphtech was more complicated and has more parts. Has individual wires for each saddle to run, which plug into a combiner or pre-amp. Has many more options, as a result. I still did the full install (including re-wiring the magnetic pickups and controls from scratch) the day of an out of town gig, the first night of a stretch of 5 gigs, and it worked perfectly fine.
Both sound great. Hard to say what tonal differences there are, if any, as the guitars themselves are so different in construction and unplugged tone. The Fishman is actually a bit louder than the Graphtech, though I may be able to fix that with a trim pot on the Graphtech pre-amp. The Graphtech has a nice feature of being able to still get piezos through a mono cable, you just have to use an optional switch or adjust the separate volumes to use one sound at a time. The Fishman requires a stereo cable, in the current set up I have, but it's 100% stealthy and is really hard to tell that it's not just a standard Tele just by looking at it or playing it through someone else's rig.