Would you rather... a seating chart question

Amonite

It's usually nicer to split the groups into two tables, as it allows you more leeway in seating other guests.  For example, you could put some relatives or a two couples to round out the table, so that everyone knows at least one other person. Try not to split people up more than you have to, but seating is a delicate balance.  It's never going to be 100% perfect for everyone - but a solution where everyone is by 1-3 people they know is better than a solution where half have tables full of friends and the rest of the tables match up perfect strangers.

You can always put friends at tables 'next to' each other as well, which allows for a lot of mingling/talking.

scrunchythief

I'd also consider the mobility of the guests involved.  If your guest(s) will have more difficulty getting up from an uncrowded table, a more crowded one might be very hard to navigate.  

However, if it was me and my group of college friends, I know we'd rather be together.  You should've seen the tables we'd cram into at the cafeteria (with backpacks, laptops, etc. too!)  Could you ask the guests in question what they prefer?