No simple answer to your question as there are many determining factors to deciding on which auction house to choose.
First and foremost I would research the prospective company in regards to their commission rates, previous auction results, policies and overall satisfaction from sellers. Who you chose would depend on the material you are trying to dispose of. The rarer the item the higher profile auction house you will need to the the most exposure.
If you are fortunate to have one close to home that also frequents shows and has a brick and mortar business, this would probably be your best bet for usual run of the mill items.
My first experience was above average in that I actually received higher bids on items that I could not find local buyers for. Overall I still lost my shirt so to speak having sold $700 in OIP items for around $460, but I knew that going in and accepted the fact that RCM products in particular are a horrible investment.
Good Luck and Happy Hunting!
