But not when it comes to basing my trust on the autopilot to get me there safely. At least not without a 'section by section' review of the course it has chosen. And if I'm doing that I might as well just plot the course on my own anyway.
The OP is interested in Garmin vs Furuno. With a new boat on order I'm shopping. I wasn't going to go there and get this off track, but this autopilot / auto-route discussion kinda takes it there.
I agree with what pretty much everyone agrees on, and that is all of the top brands are pretty good these days. But you still have to choose one, and find a point(s) of differentiation. One of them is auto-routing.
Pretty much everyone is going to get autopilot these days, even if only to use it to hold a straight line course to a compass heading for a time. So if you are going to have one why eliminate the option of auto-route completely? I don't get that part. Preserve the option. (Unless your favorite brand doesn't offer it, but does have some other killer feature important to you.)
So Furuno doesn't offer it. Garmin and Simrad do. Just playing with demos and watching videos there are a couple of important issues that differ.
First, the Garmin auto-route only works with a Garmin autopilot controller at the rudder. Because Garmin autoroute uses some proprietary smoothing of the turn radius that somehow only works with their own MFD hardware attached to their own rudder control unit. This may not be an issue for someone, but might, so I mention it.
Second, Garmin can only plot a course from where the boat now sits, to the end point you select. You cannot, for example, plot a course that begins once you exit an inlet, or some crowded chaotic stretch near your marina. You cannot plot in advance a multiple day trip and save day 1, day2, and day 3 as different saved trips. You cannot then use it to calculate a trip if you are wondering how long between two points that are nowhere near you. With Simrad you can. You select the course beginning point, and end point.
Third, I agree a course plotted in autoroute should not be followed blindly along inland waterways. So making adjustments to the autoroute before hitting go has to be user friendly. From what I can see, both are reasonable for this need, but I give the edge to Simrad.
FYI the Simrad autoroute feature only works with Navionics charts downloaded into Simrad. I have no idea whether one can use the Bob423 tracks if that interests anyone, since as I recall his are done in Aquamaps or something.
There is still one aspect I do not have a good answer for with either brand. With both there is a helm station control pad in addition to having all controls within the MFD. That seems to me to be an unnecessary redundancy. It takes up valuable space at the helm station for the extra pad, and the pad isn't cheap. However the pads do have one very valuable aspect: a big red button to shut off autopilot when you want it off, and want it off right now. With the MFD's so programable these days I am only guessing one can program your display screen to leave up the big red off button. Surprisingly, I cannot confirm that yes or no including in discussion with one Simrad rep in a booth.
In a related manner, if one temporarily chooses to veer off from a programed course (to avoid traffic, crab pots, etc), HOW does it return you to the course? There are options buried deep in the program options trees. Return the boat to the point of departure from the course? The straightest route back to the course line? The straightest route to the next waypoint? What you might want to do can differ greatly depending on circumstances and being able to have that up on the MFD in a box would be great. I don't know what's possible. Importantly, think through what this means when you grasp the point above that the course plot begins at your marina slip, if you are programming it before departure, as most would do.
Last, there are a max number of waypoints in a course. This won't be an issue tooling down the Chesapeake with maybe a half dozen or so waypoints on the trip. Down the twists of the ICW, it might be. I have yet to grasp whether the limitations are meaningful, for either brand.
If anyone has info that says I'm wrong about any of these feature differences, believe me I'm all ears and would appreciate being set straight.
My second reason for Simrad is forward looking sonar, but that's a different topic.