I had to change out the carpet on my Chrysler Grand Voyager a few years ago following repeated soakings from dragging in water and snow after a bad winter. It turned out that water had pooled in the wood under the carpet and it began to rot.
I went with vinyl flooring and whilst it's much easier to keep clean and sweep out, it does unfortunately make it quite a bit louder inside. I also had to adjust the automatic tie down slightly as there was no 'give' on the vinyl under the wheels as there was with the carpet, so the distance between the floor mounted spigot and the tie down unit (attached to the chair) had changed. I would say that for me sitting in the powerchair, the vinyl floor does feel more solid under the wheels and gives a much harder ride
Inside the car now feels more van like and less refined .... but the trade-off is that water now lies on the surface and can be wiped away rather than finding a way through the carpet to soak and rot the sub-floor!
I had hoped to use the dimpled black rubber flooring which John has linked to, but the converter didn't have it available at the time, so I went with the vinyl floor they had in stock.
Cal