Taste is a very subjective thing. I am not sure it is possible to quantify exactly why one is better than the other. I have heard some say they prefer the basic basket they got with their machine, that is unusual though.

Whatever works for you I guess.

 

I have had issues with my 18g VST basket on the LR with headroom when I dose 18g regardless of roast level of bean I use so perhaps that is the cause of your issues. I also have a 20g IMS basket but that seems to want 20g+ to work nicely.

Basically, take the dosage on the basket with a pinch of salt. If you have no headroom thats not a good thing as far as I know.

 

As I understand it, VST baskets are intended for light roasts, which are naturally hard to extract. Because VST baskets have larger and more holes than normal baskets, the user must grind finer for the same flow rate. The finer grind exposes more surface area to the brew water, and this produces higher extraction.

I don't know how this affects darker roasts, as these extract relatively easily, anyway.