Midfield presence, is it important?

So, how important is midfield presence to an army in the game of 40k?

Well, we can first look at the pros. You have a shorter range to points on the board (objectives, opposing forces etc.) and you increase your threat range to cover a rather large area. This does give an advantage to almost every army. There are few armies that can really deal damage efficiently just from a corner of the board, and that can snatch objectives effectively without midfield presence.

In addition, midfield supposedly gives you the advantage of better using terrain. This is especially true on boards that have losblocks in the middle of the table etc.. The theory is, that by being close to the terrain, one can take cover from it and shoot without giving cover, or atleast only pop out of cover once you want to melta stuff etc.. In my view, this is more situational, but a good point to keep in mind.

Having a strong midfield presence not only gives advantages to you, but puts your opponent at a disadvantage. If you can dominate midfield, your opponent will have more inefficient threat ranges and a harder time making it to objectives.

On the negative, some armies suffer from giving away side armour shots. This depends on the army, but can have a major impact on the game. It also puts you in harms way, placing you essentially within small arms fire. Sometimes it is better to preserve your forces, deploy back (or possibly even refused flank) and try to outshoot your opponent (or outlast him). Some armies are better at staying back and disrupting the opponent (like tau). Against CC armies, this is especially true. You'd rather hang back and shoot for as long as possible.

My observations have shown that most armies gain an advantage from holding the midfield. Most marine armies are unaffected by side shots (due to the nature of a rhino hull) and armies like DE Venom Spam need to move up to get those blasters in range. Towards the end of the game the player that holds the midfield has an advantage in objective games, as he has more objectives within reach, and can extend his threat range further to stop the opponent from taking objectives.