let's compare monsters:
Valkurm Dunes:
Hill Lizard lvl 15-18
Goblin Ambusher, Tinkerer and Butcher lvl 17-20
Snipper lvl 18-22
Damselfly lvl 20-23
Goblin Gambler, Leecher and Mugger lvl 22-25
Beach Pugil lvl 23-26
Bogy lvl 28-30
Buburimu Peninsula:
Sylvestre lvl 15-18
Goblin Ambusher, Tinkerer and Butcher lvl 17-20
Snipper lvl 18-23
Bull Dhalmel lvl 20-23
Goblin Gambler, Leecher and Mugger lvl 22-25
Shoal Pugil lvl 24-28
Bogy lvl 23-25
Hill Lizard vs Sylvestre
Sylvestres are mandragoras. The same mandragoras that people like to kill in the jungles. They dont have AoE attack and they dont petrify people. Easier to kill than lizards.
Valkurm Snippers vs Buburimu Snippers
Buburimu Snippers are 1 lvl higher but that shouldnt be a problem. That even helps because people can lvl off snippers longer.
Damselfly vs Bull Dhalmel
Bull Dhalmels hit hard but they dont have AoE attack. With 2 blink tanks they are easy. Even with WAR or PLD tank they are more managable than Damselflies
Beach Pugil vs Shoal Pugil
Shoal Pugils are higher lvl. That means people can stay there until lvl 20 before going to Jeuno. They can outpost warp from there to home city and they can start chocobo quest right away when they get to jeuno
Valkurm Bogy vs Buburimu Bogy
Buburimu Bogy are much lower lvl and they can actually be killed by xp party there. Even if they decided to run away from bogies they have high chance of survive unlike valkurm bogy.
So Buburimu Peninsula offer safer and better place to lvl up compared to valkurm dunes.