My felings as of late is to give almost anyone the benefit of the doubt,if he/she is passionate and seems to know a bit about "things" audio/music.Even if I am really sceptical about something,I no longer think I can gain anything by being a contrarian,other than receive contempt from some posters,SO I just stay quiet.Mostly!!
The business of vacuum,I know very well,as I have lived with vacuum units(about four tables)over some twenty years.If anyone thinks it is hard to keep a platter clean,while owning/using a good vacuum table they are greatly mistaken!
I have NOT had a single pop or tick,that I can say with certainty happened from a vacuum seal,in my 2500 LP collection.However I DO have a dedicated(locked) audio room.My friend has a dusty environment,and has had vacuum for about fifteen years,and has almost no noise issues as well.
The solution to keeping the platter clean,from my expperience,is to simply brush the platter surface with a "facial make-up brush"!You know,the type of brush women use to put rouge type make-up on their face.Very inexpensive,at around five bucks(though there is a typical rip-off audio company selling one,made of horse hair for 80 dollars)....That's it!!..No noise problems,unless you are careless.
As to the sonic impact of vacuum,to me it is a common sense attitude,coupled with "not even having to be a careful listener",it is just "that obvious"!Inner details stand out in bold relief,and if you have one of the elite arms and cartridges,you will notice something special,and in less than a few platter rotations.This is one feature I can unquestionably state is just "fabulous to have"!You want to take advantage of that fabulous platter composition you have?Well,it makes good sense to "almost" bond the LP to that platter,which eliminates any air pockets under the disc from vibration during play.No standard clamping system will give this result.AND some are pretty good,but the brass ring belongs to the finest vacuum systems.With these you truly have a disc that "truly" weighs as much as your fancy platter.Not a bad thing.
That is definitely "not" to say it is a "must",but if you have lived with it for as long as me,you don't want to be without vacuum....Personally I believe (though the subject is still open to debate,to anyone,"except me")that the non vacuum mfgrs have an easy dismissal of vacuum,as more of a marketing tool,than actual confirmation of it not working well.It certainly would not be easy or cheap to add to existing products,but had the CD not come around,I think there would have been a bigger push towards vacuum tables.....Just some thoughts-:)
Best.