Over the years, the methods by which armies are deployed on the table top have varied strongly. Once upon a time, they were all just lined up in a row and directly faced off against each other in a pitched battle style reminiscent of Fantasy armies arrayed in long rows and columns. For a young mind, the idea that one could do this using the short edges as well as the long edges was novel to me. Then there was the battle in the back of the Rogue Trader rule book where the main force was surrounded and the enemy came in from any old angle. This also was amazing to my young impressionable mind.
What these kinds of deployments have in common is symmetry. Whether this is the long edges, or in the centre of the board, they are almost always rotationally or mirror symmetric. I really favour this kind of set up. Indeed, one of the biggest compliments that I can give the 30k battle ethos is that each and every one of them are symmetrical in some manner. One of the core examples that folks might not have seen much of is below (Clash of the Line).
Increasingly, there are more and more deployments that feature somewhat asymmetrical deployments. Or worse: terrain that is very biased to a particular deployment zone. Now, of course, that is just realistic at some level. However, for a game such as Warhammer 30,000 where everything has been so very carefully balanced in terms of their points value on the board, I think there is a lot of merit in retaining symmetrical deployments as much as possible. Not only is it simpler, but it means that the players start on a roughly equal footing supposing that the terrain is also reasonably balanced and well positioned. Symmetrical deployment is therefore a concept that I have really come to like - doubly so for tournament play, even though I also like the narrative of unequal forces and terrain in general.