manta wins any prep match pretty easily. he's actually very smart and has access to some decent tech if given time.
in rd 2 the range advantage is still a big deal. he's tagged arthur with his eye blasts and arty is faster than scorpion imo. if scorpion can close the gap, manta has still gone 1on1 vs arthur for prolonged lengths of time. somehow. still. that would be more in favor of scorpion imo. if he can avoid the water of course.
rd3 favors scorpion the best, but range remains an issue, so it's basically rd2 all over again. if he gets in close he can win (and take a majority imo) but getting in close given standard starting distances would be pretty tough.... decent match up though.