I can't compare all three but I purchased the loop style carpet from Moss for the 4A. It's not wool but didn't cost like wool either, think it is their mid-grade carpet and appropriate for the 4A. Complete and very nicely made, fit is perfect.
For the 3A, I tried VickyBrits cut-pile deluxe kit. Although the carpet pile is nice and thick, there were bald spots in the nap and the cut edges were very roughly cut. Also the edge binding was cloth type junk and also poorly stiched, quite poor compared to Moss so I returned it and ate the shipping costs. I then purchased the Moss cut-pile kit. The pile is very short compared to VB but much denser nap and the fit and edging is much better than VBs, nice vinyl edging. Still not totally satisfied with the nap but it was 1/2 cost of wool. I hear (no personal experience) that the TRF magic wool carpet is the best but pricey.
None of the carpet or interior parts and seat covers I purchased from Moss or VB had any doc on how to install it.