Though its chassis supports a number of variants fielded throughout the Legions, the core Sicaran battle tank remains a versatile favourite. The Sicaran is one of the most advanced armoured units in the arsenal of the Legiones Astartes, a fast-moving destroyer tank designed to outflank enemy formations before unleashing an overwhelming onslaught of mid-range firepower. I recognize the fact that certain lists it would have a place, though I don't play those kinds of lists.The Legiones Astartes - Sicaran Battle Tank from the Warhammer: The Horus Heresy range provides a highly detailed model tank for your Legiones Astartes army. IMHO, Whirlwind Scorpious > Sicaran Arcus. I have a lot of experience with artillery and Scorpious though. I have no practical experience with the Arcus, as no one in my meta has one. but that's a pretty tall order for a tank that has to have line of sight to its target for two turns. The Arcus gets 8 shots when it doesn't move. If you specialize the tank and your opponent doesn't bring the unit you specialize for, you just wasted those points- points you could have spent on multi-melta upgrades for your Rhinos, or a P-fist on your Sergeants.

If you bought all those warheads, you'd have a 270 point tank- more than a Land Raider without it's durability.

The Arcus has to pay points for all those special warheads, which are nice, but they make it into a 'Jack of all trades' tank. Everything it shoots is a S8 AP3 3' blast, and when it sits still, it can fire 1+d3 of those shots. It doesn't require line of sight to shoot.

You can field two Whirldwind Scorpious for the price of one Arcus.

Sicaran battle tank: