It really depends on what you are doing. (Do you work in VFP? If so, this question is not unlike "Do I use Scatter and Gather or Insert Into? Do I use Scatter Memvar or Scatter Name?" It all depends.
Here are some very very general guidelines:
-- Arrays
Take less memory than collections
Generally quicker than collections
-- Collections
Easier to code than arrays (built-in Add and Remove and retrieval techniques)
Easier to pass around among functions/subs
There are other factors too, but these are the ones I consider most important. Hope this helps a bit.
The whole problem with the world is that fools and fanatics are always so certain of themselves, but wiser people so full of doubts. - Bertrand Russell
