Why "or" if they don't do the same thing? Valhalla Ubermod is the plug-in that's oriented toward modulation effects like the Dim D. Vintage Verb is oriented toward reverbs and certainly isn't expensive to buy it and something else. ERS's vintage style reverb is the empty 250
When it comes to emulating old effects of course it depends if you want to come as close as possible to a now classic unit or just want that type of thing with perhaps more options.
I'd definitely say Valhalla gives you value and more options. ERS gives you emulations of one specific unit
The Dimension D was a "subtle" chorus where you hear more of an added stereo dimensionality than typical chorus modulation per-se. Never heavy and swirling. Definitely not a room reverb or anything like that. Not exactly an all purpose tool, can't use it on many things, but it really adds something special to synth pads and some instruments.