Shooting vs Assault

As a Blood Angels player, you probably have a good idea of my thoughts on shooting and assault. Specifically, that shooting is an auxiliary to the assault. Allow me to explain how I think shooting and assaulting stack up.

Shooting
First of all, you need LOS for most shooty weapons. So if you are playing something with a LOT of terrain, a clever player can essentially neutralize enemy shooting (and their own in the process). Also, you can't shoot into an assault.

Second, shooting just doesn't get the job done. Assuming you have a group of 10 tactical marines across from some 'zerkers (also a 10 man squad). Your within 12", so you decide to rapidfire with your bolters. Standard 3+ to hit, 4+ to wound with a total of 16 shots (because your sarge and special weapons guys are being excluded from this example). In total, this gives you a 33% chance of wounding a model, and a 22% chance of killing a model. This translates to roughly 3-4 dead 'zerkers (on average). That's gonna be a lot more attacks coming back your way, because they are going to move up, shoot with boltpistols (likely killing a single model), and then assaulting. This gives them 4 attacks each on the charge, bringing the total attacks to either 24 or 28, depending on how many died. The tac squad is responding with a meager 10 attacks in return. Guess who wins that one...

Third, I haven't seen any special rules for shooting, other than markerlights or equivalent. Great, you can increase your ballistics skill. On the other hand, one of your models isn't shooting that turn.

Assaulting 
Why does assaulting rule? First, you don't need LOS. You just move up, charge in, and get bloody.

Second, assault guarantees results for either you or your opponent. Eventually, one group of models will die, and the other group will seize the day. Unless you have some of the rare special rules that allow you to leave combat whenever, your models stay in combat until either you or your enemy is dead. Translation: results.

Third, assault has lots of different rules. First, offhand weapons, chapter banners, and assaulting each give a free attack. However, there is no way to increase the number of shots you take. Sweeping advances and fearless wounds also take a huge toll upon the enemy, something shooting isn't able to incorporate.

In conclusion: assaulting is far more dangerous than shooting. Shooting certainly has a place, (softening deathstar units, popping transports, avoiding getting locked in combat with dreads, etc) however, it doesn't have the mass killy capabilities of assaulting.