As you can already see, you're going to get numerous responses in the hashes-or-vars question. No matter how "leet" the replies look, I think you shouldn't take anything for granted. Benchmark both ways and make your own conclusions.
Regarding what's fast/faster/slower in scripting, generally, I'm afraid the only real picture you can get is by your own experience. Of course, taking into consideration what others have to say is always good, but secondary. Following rules regarding performance without understanding (or without having tested) them yourself is pretty much useless in the end.
