On the Tazer, the price is the obstacle - $300 is a bit steep. Although, the nav disabled is really starting to bug me. Not sure if it bugs me $300 worth yet though.
It also adds some other stuff that we can do with Alfa (a small subset of common tasks ie led, backup cam, tire size, tpms stuff, etc), and a few other things like brake line lock for instance, but one that does stand out is it allows side mirror auto fold/unfold on shutdown/startup we can't do with Alfa, IF you leave the Tazer in the OBD plug. I already have PowerAmp Steps controller plugged in there, (Plus the Tazer unit is kinda long, it would jut out/down into the footwell more than I would like it appears) but I suppose I could add one of those inline bypass cables to add a 2nd OBD port.
Oh it also can disable Sirius Weather warnings, which can get annoying at times b/c they keep coming up over and over sometimes. It also appears to do Global Windows UP from the keyfob which we can'd do with Alfa either.
Does it sound like I am trying to talk myself into buying one lol...
EDIT - Actually it's $249, not sure if the price dropped or I misread it last time I looked, but I though it was $299 before.