I haven't seen in the forums / general discussion about a pin point location for - best way to level pokemon to lvl 100 - so I wanted to inform the general public with what I know.
Currently (according to my findings - soz if this is exposing some people's secret location ) the best place to level is the ENTRANCE of the Victory road in Hoenn.
Step 1 - Find a sweet scent poke and Max PP (32 PP aka 6 horde spawns)
Step 2 - Locate the entrance of the victory road in Hoenn which has a PC right next to it.
Step 3 - Teach your leveling poke Surf, Hyper Voice, etc. type AOE moves.
Step 4 - Equip Lucky egg + Donator Status (even if you don't have these the exp gain is much more/faster than the other zones)
Step 5 - With the setup above Collect 7.5k-8k experience per horde clear.
*Tip* If you want to maximize Experience gain, skip Loudred packs and just focus on Golbat, Medichamp packs.
Thanks.
P.s if you know another location that would compete with 8k exp per horde as above mentioned, please do share.
- Seqqs