I think there is no such thing as the best carpeting plant.
Each tank is different so one should chose a carpeting plant which is most suitable for his/her tank.
For example there are plants which need strong light, CO2, ferts and soft water, which others will grow brilliantly in low lights no CO2 n very little ferts. Chose a plant that suits yr aquarium conditons.
Marsilea Minuta, Staurogne Repens, Sagittaria subulata are undemandng compared to Hemianthus Callitrichoides, Utricularia Graminifolia, Elocharis parvula, Glossostigma Elatinoides.