I have Labradar, Magnetospeed, and ordered a Garmin.
My LR has been great. I use the inertia trigger 100% of the time (mainly for consistency) but other than that it's how it came and has been very reliable. The 4000 FPS speed limit has become problematic with some of the small bore magnums I'm working on (17-250AI, 20 WSSM, 22 WSM).
Magnetospeed works fine for the laser rifles. I don't have a jig to mount it on the stock, what I'm using it on it's NBD to shoot a few with it strapped on the barrel. On a few of my very large magnum hunting rifles that would be deal breaker, I'm not wasting shots on those barrels to get velocities so off-gun like LR (or Garmin, etc) is a must for those.
Looking for the Garmin to mount on a diving board over the scope on an ELR rifle. Appears very promising and looks nifty, but for me it's an unknown quantity at this time.
I'm not getting rid of the LR any time soon, it has a good set of features and I don't see anything about the Garmin that's straight up better, just a smaller package doing the some of the same things.
I drive an almost 20 year old truck, shoot 30-06 and 6.5CM, but still watch The Longest Day in the original black and white. I'm fine with new things, they just need to bring something to the table other than a tweak to claim the title of "better". 6.5CM isn't "better" and I doubt the Garmin is either.