It's a rather emotional subject in many ways. Doctors at home will swear that you MUST take anti malarials, then the ones in the countries will tell you "under no circumstances".
There are theories of the prophylactics "masking" early symptoms and making treatment harder due to delayed diagnosis, aside from the health issues from long term use of the drugs.
Some companies insist on use on pain of being fired if you get malaria and don't have the stuff in your system.
If you do get malaria, the treatment where you got it will be the most effective and skilled.
Personally, I have the pills with me at all times and I decide when I get there whether I will use them or not, dependant on season and number of known cases of malaria in the area. I also have a self-test kit in case of emergency.