Don't listen to the silly universal ones..
You want the best mount?? I'll tell you what the best mount is!!
It's a case.. That's right.. After riding 150 miles a week for many years and having all sorts of cycle computers, I wanted something CLEAN!! I bought a two piece case, like an otterbox (I forget the brand) and simply mounted the plastic to a typical ring clamp on my bike. I drilled/glues into the clamp so it was secured as could be!
When it was time for ride time, I would simply slide the rubber case (the second piece) around my phone than secured that into the mounted plastic case (The first piece)
It was 100000x better looking, it was actually USEFUL as you could use it while riding, it was also extremely secure! and could never come out without the proper bending and normal way you would take a phone out.
This was mounted so I could adjust on the fly, I used one of the garmin computer clamps I had laying around that would twist sideways and up and down. so when I got going I can adjust the phone so its angled with the wind and won't be a mud flap