I am lucky enough to play most of my games on a 8 ft x 5 ft board. This allows for many more tactical options - especially when it comes to maneuvering your forces. Not only can attackers formulate more elaborate plans, defenders also have more things to consider - particularly when deploying troops.
There are more outflanking opportunities, chances to focus your push against one side of the enemy forces and the possibility of splitting your enemy's army in half.
The reason being that both sides must consider their unit placement much more carefully. There are usually enough units in a 3000 pt army to cover your full frontage but this quickly changes once units begin routing or a destroyed.
This situation can sometimes lead to both armies 'winning' on opposite flanks and then a final confrontation at the end.
A larger board also gives more chance for a 'losing' army to regroup and strike an enemies flank in force, is successful he might even force a draw by possessing victory point terrain or table quarters.
The main issue with smaller boards is they tend to be full frontal assaults with little thought given to tactics on the field of battle but lots of thought put into army selection.
There are only really 2 draw backs to a larger board:-
1) You need more time to play and
2) Victories tend to be less decisive unless played to the bitter end.
One last point, if you have the space to use a larger board make sure your arms are also long (or stretchy !) enough to move your troops in the middle !
Thanks for reading.