I do not know much about the details but apparently you can fight the Tigrex and the Rathalos with Velociprey as trash mobs in that game. Felynes come out and toss you boxes with rations and ammo plus you can cook the rations just like in the Monster Hunter series.
And yap, MGS: PW has some extra missions, which are basically crossover between MGS and MH series. Note, these are EXTRA ones, and are ~not~ in the main story.