@trixiegirl Hey there.
I wish I knew the answers but I'm just wondering like you.
Here's what I think right now (but have no way of knowing for sure):
I'm not interested in trying any other vibration plate because Dr Clinton Rubin is the man in terms of vibration and bones. He spent many many years in this area doing research. He has developed or helped develop two devices based on all that research. If those devices do not increase bone density I'm not going to try others devices who did not do this research and had no special interest in bones. For them it's just an add on means of increasing sales.

That said your logic that Marodyne may not be strong enough may be correct?
But here's how I think about that - Dr Rubin made a great deal of effort to hit the sweet spot in terms of what type of and how intense a vibration to use daily without endangering your retina and other areas susceptible to damage from vibration. Again he made that effort and if he thought more vibration might be unnecessary or dangerous then he's the one that has put the most effort into studying this.

As for Osteostrong, I do not find strong evidence in their favor. Some interesting ideas I think but their own studies (two I think) are tiny. The only substantial study I know of done by Belinda Beck and company in Australia (yes the same group that did the LIFTMOR and VIBMOR study) showed inferior results with the Osteostrong device compared to three weight exercises and one jump drop exercise. See the LIFTMOR-M trial here:
https://research-repository.griffith.edu.au/server/api/core/bitstreams/812c5a89-0876-4237-b12d-a4cbab2e3ec6/content
Machine-based IAC (that's using the first "Osteostrong device developed" exercise did not result in any significant improvement in bone strength at any skeletal site examined, but may mitigate age-related loss of indices of bone strength at the distal tibia and radius."

I hope this is helpful without being a downer. For myself I stopped the Marodyne and I'm doing a modified version of the LIFTMOR protocol twice weekly and other types of exercise on the other days of the weeks.