I've got an Athlon my mates got a Garmin, we've used them side by side and the Athlon tends to read a few FPS higher but i think its picking the bullet up faster than the Garmin is.
The Athlon always has a reading on the screen first.
Screen size the Athlon is slighter bigger and I think is clearer to see. The stand is metal unlike the plastic one with the garmin, the Garmin blew over In the wind, the Athlon didn't.
My mate had to spend another £30 on a case as his didn't come with one, the Athlon comes in a purpose made case.
Mines been faultless and hasn't missed a shot, it's been past round the range for anyone who's wanted it, it was picking up black powder pistol calibres, air rifles, someone's 243 who was sending out 55g stuff out at nearly 4100fps!
I was in your position a little while ago and thought the same thing, I'm glad I got the Athlon as I personally can't see where the £170 difference is. £200 if you add on the case.