Hi, depends on what you're looking for.
Central is one of the busiest divisions with high crime rate
despite being the smallest division of 3 NPCs (Bukit Merah East,
Rochor, and Marina Bay). Tanglin division is much bigger with 5
NPCs (Bishan, TPY, Bukit Timah, Kampong Java, and Orchard) and not
all of their NPCs are busy.
Are you looking for a challenging and fast paced environment? Go
for Central division. No matter which NPC you get posted to in
Central, all 3 are equally busy. Rochor NPC's biggest headache
would be Mustafa and almost the whole of Little India. Bukit Merah
East NPC covers a number of HDB blocks and Chinatown which is
enough to keep officers there busy. The unique NPC would be Marina
Bay where you deal with the working office population and the party
goers instead as there are plenty of entertainment outlets (pubs,
clubs, KTVs) under Marina Bay NPC's jurisdiction. The only
residential areas are occupied by the richer percentile of our
population (elites everywhere). As for Tanglin division, Orchard
NPC is the busiest one and their terrain is similar to Marina Bay's
with all the entertainment outlets and expensive residential areas
except that it is much more compact there. As for the other NPCs in
Tanglin, I am not so clear on their terrain but they are definitely
not as busy as Orchard NPC.
Also, you should know that you cannot choose your NPC so
choosing the right division matters a lot.