La-15 (La-174) wasn't exactly a direct competitor to the MiG-15, that was the La-168, which used the Nene clone RD-45. La-15 was smaller and used the Derwent clone RD-500. La-174 was a developed as an insurance policy for the La-168, which suffered from non-availability of its Nene engine; supposedly Mikoyan used his brother's influence in the Communist Party to secure one of the original Nenes to put in the I-310 (MiG-15) and so gained a good 4 month lead over the La-168. This was critical, and in the absence of any major flaws in the MiG-15 proved decisive. La-168 was generally better, but not by enough to justify production.
La-174 was placed in production as La-15 but only 225 were produced; the main reasons were its greater production complexity and that the Nene was quickly developed into the much higher thrust VK-1, while the RD-500 did not have the same development potential, so the MiG-15 had much greater growth potential.
