I have a Garmin Edge Explore 2, a brilliant little unit that once you get over the initial learning curve is a great GPS unit with brilliant battery life.
My personal opinion is that both Wahoo and Garmin make fantastic head units these days, the current crop of Garmin Edge units are easily comparable to the current Wahoo units and rather than a straight Wahoo vs Garmin it should be a case of what features do you want and base your decision from there. One of the reasons I explicitly went with Garmin was because for the most part, I don't need to use my phone with it which given that I ride in a lot of areas without phone reception is a blessing.
I went with the Edge Explore 2 over the 540/840 because I don't need or want all of the training stuff that comes on it. The possible downside to the Explore 2 is the touchscreen. I prefer that, but many won't, especially because it's hard to use with gloves on.
With the Explore 2 you do need a Garmin account, but that's no big problem, you will also need the Garmin connect app on your phone. You also need to sync whatever ride creation software you are using with Garmin, again, it's a one time deal and simple to do. When I first switched the Garmin on I plugged it into my computer and it needed a big update that took a while, but after that I rarely attach it.
With routes I create them on Ride With GPS, then "pin" them. All I then need to do is open Garmin connect on my phone, switch bluetooth on and the app syncs with the Edge Explore 2 my route pops up and I'm ready to ride. It takes more effort to type and explain it that actually do it, it really is seamless and then my phone goes off and into a bag for the rest of the day.
One last thought was I was really taken aback by how small these modern GPS units are, when you are used to the bigger phones we have these days. The Explore 2 is bigger than the Edge 540/840 and to be honest the screen is only just big enough for me!