Laser Pistol vs All Predecessors
If (as argued elsewhere) either the Heavy Cannon or the Auto Cannon is the best standard primary squad weapon at the very start of the game, what to do when the Laser Pistol is available? (Presuming that Laser Pistols are researched before any other replacement standard squad weapon.)
Unfortunately I think the Laser Pistol is so powerful that it immediately displaces both the Auto Cannon and the Heavy Cannon as the primary combat weapon, and forces both into a support role. The Auto Cannon moves forever into a specialised role only. The Heavy Cannon will languish on the shelves, at least until much more heavily armoured enemies arrive on the scene.
As a support weapon the HC will be restricted to clearing hard terrain (with AP and HE), and delivering explosive rounds (including against terrorists). On a terror mission, it might be partly restored to its earlier value to minimise "friendly fire" against civilians.
In pure firepower, the Laser Pistol is more powerful than any starting fired weapon, other than the Rocket Launcher, against all aliens except the Reaper. HC-HE and AC-HE are about 4 times more effective than Laser Pistols versus Reapers (and twice as effective as Laser Rifles, even). Otherwise, the Laser Pistol significantly exceeds the Heavy Cannon and Auto Cannon (and Rifle and Pistol) in general-purpose firepower, and far exceeds it on versatility, weight, space, ammo, speed and flexibility.
In theory the HC-AP retains superior armour-piercing capability but in practice this only applies to destroying key items of hard terrain. The main heavily armoured enemy, the Cyberdisk, is better dealt with by Laser Pistols rather than HC-AP - as are all more lightly armoured opponents. AC-HE and HC-HE are almost completely ineffective, but Heavy Rockets are still the most effective, more so than Laser Pistols),
The main drawback of the Laser Pistol is its poor accuracy, especially when used in continuous auto burst mode (as is optimum). For this reason it might be good to retain Heavy Cannon for situations when accuracy is critical, since the HC is the best sniper weapon (out of the starting weapons).
For one-shot/one-burst kill probability (to prevent reaction fire) against the typical Sectoid or Floater targets the AutoCannon is about the same as the Laser Pistol in all modes. The aimed Heavy Cannon (AP or HE) is significantly (50%) better than all other starting weapons apart from the Rocket Launcher (which in turn is 50% better again). The aimed Heavy Cannon of course has the additional benefit of reducing collateral damage.
In summary, once the Laser Pistol is deployed:
- The Laser Pistol becomes the primary standard combat weapon.
- The Auto Cannon is relegated to specialist roles (Illumination, fighting Reapers, clearing light terrain, close range shock work if you have good armour).
- The Heavy Cannon is relegated to the roles of sniper weapon, fighting Reapers, and hard terrain destruction. The Heavy Cannon retains more usefulness than the Auto Cannon.
- The Pistol becomes obsolete except as a secondary weapon during the transitional period when Laser Pistols are too scarce to give to everyone.
- The Rifle becomes pretty much obsolete I think. The Laser Pistol has more firepower and better first-shot/first-burst kill probability, in every mode. Possibly useful in situations such as scouting a Terror site, where the extra accuracy helps to reduce collateral damage, balanced with the relatively quick fire & movement.
- Rocket Launchers firing Heavy Rockets retain most or all of their starting role as X-Com's "ultimate weapon".