Is there a purpose/benefit to chilling your beer prior to siphoning to a keg or bottling? Exluding increased gas dispersion into colder liquid during forced carbonation.
Chilling or "Cold Crashing" your beer prior to kegging or bottling helps any yeast and sediment to drop from your beer to the bottom of the fermenter. This helps to give you a clearer beer with less chill haze and sediment.
I don't really get this question. Where are siphoning it to? If you mean to go to the bottling bucket, then I would cold crash while it was still in your fermenter. If you are transfering directly to the keg, then I would still cold crash while in the fermenter.
Another reason why I cold crash (at least in the winter) is to save some energy in my kegerator. If I leave the fermenter sit in the garage for a day or two when its cold outside I get the yeast/haze fallout plus the added bonus of my beer already being close to the temperature in the kegerator. This is especially beneficial to me since I use a cold box extension on a mini fridge for my under-counter-rator. The less work I make that compressor go through the longer it will last me.
Brewing beer is the only reason I will ever like winter. The entire process seems so much easier.