Ive got two cents on this issue....
Vsti plugins dont register for the most part, which allows you to move them within the vstplugins directory, in a hierarchical structure for organization and visual orientation
for instance, you can group all your "reverb" plugins in a reverb folder, and the plugins will still work.
Dx plugins, on the other hand, are not "sortable" in the dxlistings of any program, they just list alphabetically.
I seem to remember debates about vsti plugins having a bit less overhead than dx plugins, but thats something ive not tested personally.
I load only the dx plugins that dont have corresponding Vst counterparts, because I tend to not use a lot of fx within programs that only use only dx plugins. And the solution for that would be to use a dx to vst wrapper.
So im saying I tend to focus more on using VST plugins, and use the dx ones when they dont have a vst version.