The kx-one can be competative but the price is high, parts support is low and trying to find others that run it in the US will not be easy. There is also a good chance that the out of box setup won't suit a new driver since it comes equiped with a front one-way. The sport 2 can be competative with a few hop-ups and is a solid car. The Tc3 has massive support in the US and is one of the best cars out but it probably won't be as durable as the sport 2.