Does anybody have both 32 and 64 bit versions of these installed side x side for either one or both of these?  If so, do they share samples, or are there two copies of those as well?
 
Here's the deal.  After having S-Plat x64 and the 64 bit versions of the above installed for a while, I installed Project5 2.5.1.  I skipped installing the version of Dimension that comes with P5 because I didn't want to clobber anything.
 
 

I have never installed 32bit and 64bit on the same machine but AFAIK only one multisample folder is installed for each synth. The location depends on whether the 32bit or 64bit version is installed first.
 
The P5 Dimension may be a different case on a new machine. The registry entry for DPro was renamed after the release of P5v2 and I do not believe the P5 installers know about the change. If I wanted to protect my DPro multisample folder just in case, temporarily renaming the DPro folder would prevent the P5 Dimension from messing with it. One other big difference between Dimension and DPro v1.5 is all the samples in DPro are flac files which Dimension cannot use. IIRC, one of the reasons P5 users would install Dimension was the FX chains made with Dimension did not work with DPro unless they were modified.

Good info.  Thanks