4 meter by 2 meter? Approximately 12 ft by 6 ft? I would love to play a normal sized game on a field that large!
Generally, I play on 4 ft by 8 ft. We do a lot of games on 4 ft by 6 ft. Usually, armies are in the 1500 pt to 2000 pt range. Close combat starts by turn 2 at the latest, sometimes turn 1 depending on who you are facing, deployment zone areas, and how careful people were in their initial setups. That is why I always take some close combat capable units.
On a 4 ft by 4 ft board, I would use my orks or my marines. Such battlefields really cripple the guard unless there is no cover and the guard gets the first turn... Then the guard has a chance if properly armed.
I think 5 ft by 8 ft, with 24" between deployment zones plenty of small terrain features and a few large terrain features to break of firing lanes would be most fair. It would give shooting armies a bit more room to maneuver and enable armies to choose to compress their formation in order to buy an extra turn before close combat. However, some people feel that 4 ft by 8 ft gives Guard an unfair advantage...
This weekend I play on a 20 ft by 24 ft battlefield. Two 7 player teams, each with a 3500 pt force... It will be different. My commander has requested that I leave the footsloggers behind and take an Armored Company instead. It will be different.