I have both the V2 & V3 for a .40 cal Badger. The only reason I bought the V3 was for the 6.5" extension. On the Badger I could not really tell a diference between the V2 & V3. IMHO with the volume of air the Vulcan 2 in .30 is putting out you would not hear any difference. After adding the 6.5 extension there was a big difference, but that is another story.
I have a Ronin on an FX Impact .30 and because the end cap of the Ronin will fit the V3 I have tried the V3 on the Impact. To my ear I could not tell a difference. Tells me the Ronin is the "right size" for the .30 cal Impact or equal power level rifle. Unless you want the look of the longer can, either version of the Emperor may be more suppressor than you need for the rifle. Another note, the 6.5 extension fits the Ronin, so if you bought the Ronin and wanted more volume in the can it is easy to add it.