The Ram bases are excellent. I tried their X-mount phone holder. Nothing else made fit my phone. It was OK but I never felt secure in trusting it, so I always used a tether I made from a bit of cord and put a Canadian slip knot on it. On a couple of rough roads, it moved in the mount, but it never came off. Nonetheless, I didn't like that it moved. A few more bumps and it might have come off.
The mount has an annoying habit of rotating so that I had to move the phone back to horizontal (or vertical) repeatedly. There's a recommendation on some sites to put a popsicle stick into the mount to prevent this.
The best phone holder I've found is the Perfect Squeeze, made by Hondo Garage. http://www.hondogarage.com/index.php/product/landing/perfect-squeeze-phone-mount
They make a low profile mount that attaches right to the bars, if you have that kind of setup as well as a mount for the Ram system.
I have been using a Ram X grip for the last year/30,000 miles on everything from interstates to really rough roads in Mexico. Phone hasn't fallen out yet or even come close. I did order a X grip that came with a rubber holder thing like this one: https://www.amazon.com/Texel-WebGrip-X-G...am+x+grip+mount
If you already have the X grip you can also just order the rubber band thing for a few dollars on Amazon or from Ram. After the year of being on the bike the band is starting to wear out - one or two of the web pieces are broken and it's not as springy, but I think it's done its job well and been worth the money.
I have NOT used it all the time - sometimes I forget and sometimes I'm too lazy - and still no issues. I have tried to put it on when I thought we'd be hitting something rough or were going to be at freeway speeds...
It will rotate a bit sometimes, but that hasn't been much of an issue with either of the two X grips I've used - maybe yours is unusually loose from the factory? (I haven't looked to see if it could be adjusted by the consumer.)