For convience, of course it will be kornkill, it is near Tai Koo Shing shopping centre. and a lot of different kind of transportation (but only restrict to mid n lower kornhill), cos upper kornkill (blk A, B) need to go by van, not very convience, especially in the morning, need to wait for van, but very very quiet and nice.
for HFC, isolated from other estate, most people go there is either for work or living, so to me, more safe and have its own society. Lower density.. But transportation very limied to MTR, and a few van or bus, so if you always go home after midnight, it is not a good choice to live there.
and also, see if u looking for small flat or bigger flat, if u looking for 5xx - 6xx feet, i think HFC is better, cos the living room is square shape, not in diamond, more place to use.