In channel for my vote...sorry cant post pics but it has already been done anyway. what we need is for someone to post the stick on ones. IMO the stick ons look exactly that...stuck on. you can see the outline of the plastic stuck on the outside of the window and that looks rather....autozoneish if I may.
Keep in mind, the stick on ones give a little bit more space between the guard and the window. so if your a smoker it would be easier to ash and stay dry. but you sacrifice the clean look.
stick on ones also are subject to the elements more so than the inchannels. rain and snow and wind arent the problem so much as car washes.
Stick ons are cheaper
Inchannels obviously go in the channel but are also stick on, or stick in rather. I little more time consuming to install correctly. And you really have to be careful and make sure they are installed properly or when you roll your window up the first time it could catch on the edge of the vent and make it look, well not very pretty. Luckily I was able to get a replacement free of charge.
The inchannels also sit closer to the window.
both imo are purely cosmetic. due to the shape of the KKs windows the rain guard is nearly useless because you can only open your window about 3/4 an inch before the guard stops guarding me from the rain.
these are my opinions. im sure you will like whichever you choose. they do look pretty cool.