When discussing the space size at your wedding reception there are two things to keep in mind. You need to make sure that your venue is not too small to handle your number of guests, nor does it need to be too big.
No one likes to be squeezed in to an area where they can’t move. If guests can not get to your food or your bar because too many people are in the way they are NOT going to be impressed. There should be enough space between tables to easily allow traffic flow to restrooms, bar, dance floor and food. Guests need at least a little space to allow them to mingle and move about.
Likewise, if your guests are scattered throughout an overwhelming space they are not going to feel comfortable. You want to avoid the appearance of a big empty room. Remember parties are always a bigger hit when the space is intimate and comfortable.
As a side note: When deciding on a dance floor size guests always prefer a somewhat crowded dance floor to a large open area. Make your dance floor smaller so dancers feel that they can blend into the crowd not be on display.