Serpent, Xray, Capricorn, Shepherd are all well represented in the upcoming worlds final.
That said, the RRR and MTX4 are both 5 years old give or take minor revisions but have drivers in or near the final as well.
The KM car is really nice to look at, I haven't been following their drivers very closely though but it is certainly a contender.
I don't think there is a TM car at the event?
Trends are popular and the easiest way to get started if you can't make up your own mind is to get the car that has the best support for you locally from both the shop and the racers. If 20 guys have serpent and 20 guys have xray and nobody has a shepherd, then I would pick from the first two. If 20 guys had the shepherd and no mtx4, then I would pick the shepherd.
It is tough to pick one of the euro/asia cars (any of them) and then race them here in America without help unless you are quite competent with setup and in that case any car will work for you.
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