If you aren't able to trade, Pangoro is far and away better than Machoke. Its objectively better stats give it a much easier time in the late-game and there's no real advantage Machoke has, other than a lesser Fairy weakness.
The choice is slightly harder if you can obtain Machamp, but I still think Pangoro is better. The latter has move variety that gives it more leverage against Trainers like Olympia, which Machamp notably struggles against. Machamp does have slightly higher Attack, but Pangoro's is more than serviceable -- plus its immunity to Psychic checks its 4x weakness to Fairy. Pangoro's Fighting options are somewhat lacking as the game progresses, but what it gets is good enough, unless you really want No Guard Cross Chop Machamp.
Pangoro
Ability: Mold Breaker
- Sky Uppercut (Level 52) / Brick Break (TM in Terminus Cave)
- Crunch (Level 42)
- Strength (HM) / Body Slam (Level 35)
- filler (Earthquake / Rock Slide / X-Scissor / etc)