>>50422550>>50422575At most, both will evolve a gym apart, meaning only a slight advantage for Breloom there
despite it getting destroyed by the 4th Gym right around where you'd evolve Shroomish. Around that time too, is where you would be fighting Norman, which Machoke has better physical bulk than Breloom (let alone Machamp). For the rest of the gym leaders, neither are particularly amazing with Machoke/Machamp fairing better against Winona with only a 2x weakness and having access to Rock Tomb (another thing Breloom doesn't have access to in Gen 3 lol), & Breloom being alright against Juan despite its poor Sp Def and multiple of his pokemon having Ice coverage; Machamp has a better matchup against the E4's type combination as well.
Really, the only significant thing that I see for Breloom over it in game is Leech Seed, but that niche uses for a generally frail Pokemon.