It depends on many factors, with a tournament army in mind. One must consider that every point for anti-tank is one less for something else. It's fine to field nine lascannons, until you go against a hormagaunt or ork horde. It also depends on your type of weapons and their effectiveness, and how they are placed, are they mobile etc.
For marines, assault cannons and missile launchers are great, versatile weapons - but to specialize, melta and lascannons are better. Then you have to consider balancing those out with anti-infantry. It depends if units are dedicated tank killers or mixed units simply capable of taking out a tank. And it depends on your ballistic skill.
For my current tournament 1850 ultramarines, I take: 2 twin-linked lascannons, 4 missile launchers and 2 assault cannons. All the squads have a powerfist, the termies have 2 chainfists and the assault squad has meltabombs. (On the flip side, there's 5 heavy bolters, plasma guns and flamers along with many almighty bolters to help with infantry).
I'm not sure about a formula: I'd say for 1500-2000 points, having 6-8 units with versatile weapons (like missiles) or an equivalent 3-4 units with specialized anti-tank weapons (multi-meltas, las/ML dreads, etc) for BS4 armies like marines. For different BS and other armies, this formula would obviously have to be adjusted. That's just my guess.
For marines, assault cannons and missile launchers are great, versatile weapons - but to specialize, melta and lascannons are better. Then you have to consider balancing those out with anti-infantry. It depends if units are dedicated tank killers or mixed units simply capable of taking out a tank. And it depends on your ballistic skill.
For my current tournament 1850 ultramarines, I take: 2 twin-linked lascannons, 4 missile launchers and 2 assault cannons. All the squads have a powerfist, the termies have 2 chainfists and the assault squad has meltabombs. (On the flip side, there's 5 heavy bolters, plasma guns and flamers along with many almighty bolters to help with infantry).
I'm not sure about a formula: I'd say for 1500-2000 points, having 6-8 units with versatile weapons (like missiles) or an equivalent 3-4 units with specialized anti-tank weapons (multi-meltas, las/ML dreads, etc) for BS4 armies like marines. For different BS and other armies, this formula would obviously have to be adjusted. That's just my guess.
