Fun fact alpha is obedient to a fault. Want them to run head long into a suicide mission? Alpha the squad to do it. Probably will all die but at least the order will be followed. Delta just has one mission, Ugna to the meta-hive spot and die. Charlie the reserve and bravo building sandcastles.
Can confirm I love SLing alpha, especially when a few good people are on.
When alpha follows we usually dominate the round or get killed by concentrated xeno attack.
Alpha Squad are Ultramarines, Bravo Squad are Imperial Fists, Charlie Squad are Space Wolves and Deltards are Iron Warriors.
Deltards are Black Templars.
That would imply Deltards are somewhat competent, always angry and generally doing anything useful with their free time. Iron Warriors are a far better analogies as the greatest victories Delta ever achieves is to let the xenos break into the FOB or what ever area they are defending and then flank them from the remaining fortifications.