I’ve just posted a comparison chart detailing the coverage of the tractates of the Mishnah in the Tosefta, the Talmud Yerushalmi, and the Talmud Bavli. It should prove useful as a general reference.
As one can see in the chart, the Tosefta gives the widest coverage, with the Yerushalmi and Bavli providing coverage of roughly two-thirds of the Mishnaic tractates, and different ones at that, though they do both cover a number of tractates. The only tractates to have no presence in Tosefta and the Talmuds are Abot, Middot, and Qinnim. In the case of Abot, this is likely because it was added to the Mishnah some time later than its original compilation. Middot and Qinnim were likely excluded due to their subject matter, being the measurements of the Temple precincts, and complications related to bird sacrifices, respectively.
As always, suggestions for improvement are welcome.