It's a tough decision when it comes to spending as little points as possible whilst squeezing the very best out of your Elite slots.
So I've decided to do a quick run down between the two Space Marine Dreadnoughts and sum up which is best and why.
To set the level of points to be spent, let's start with the more expensive of the two, which is the Ironclad. I'll run through each of the dreadnought variants, which weapons are good, which weapons are awful and which combinations you can't live without.
Space Marine Ironclad DreadnoughtThe ironclad dreadnought comes with armour 13 front and sides, a seismic hammer with melta gun and a dreadnought close combat arm with storm bolter as well as extra armour and 'move through cover' for a total of 135 points.
While the ironclad lacks the long ranged weaponry of the regular dreadnought, it makes up for it with heavy armour, more attacks, better movement through cover and a more specialised roll for taking out enemy troops with flamers or tanks with its close combat weapons providing its quick enough to catch them.
replace storm bolter with heavy flamer = good
replace melta gun with heavy flamer = good for twin heavy flamer fun against troops
replace combat weapon with hurricane bolters = awful!
replace seismic hammer with chainfist = seismic hammer is better, so no.
take up to 2 hunter kilelr missiles = overpriced, so no.
take ironclad assault launchers = enemy power fists will hit last anyway, so no.
Beyond upgrading the storm bolter to a heavy flamer, I'd leave the ironclad as it is, unless you feel the need for 2 heavy flamers for flushing troops out of woods.
That sets the bar at 145 to 150 points.
Space Marine DreadnoughtThe regular space marine dreadnought comes with forward and side armour values of 12, a multimelta and close combat weapon with built in storm bolter for a total of 105 points.
The space marine dreadnought has a massive selection of long ranged weapons to choose from, making it more versatile than the heavily armoured new ironclad model. Lower armour means its more vulnerable to anti-tank weapons, but equally likely to be blown away at close range by a melta gun. However, due to its wide selection of weapons, the standard dreadnought is able to adapt to more versatile battlefield roles.
replace storm bolter with heavy flamer = good
replace multimelta with
-twin linked heavy flamer = no
-twin linked heavy bolter = no
-twin linked autocannon = perhaps
-plasma cannon or assault cannon = perhaps
-twin linked lascannon = good, but expensive!
replace close combat weapon with twin linked autocannon or missile launcher = perhaps
Take extra armour = YES!
The space marine dreadnought I would take as an alternative to the Ironclad would come with a multimelta, close combat arm with heavy flamer upgrade and extra armour. That's it! It comes to 130 points, which is 15 to 20 points less than the Ironclad.
The Role of Dreadnoughts in 5th Edition Warhammer 40K
In Warhammer 40k, competitive armies have always been about maximum performance for as few points as possible. Now, I used to swear by a twin linked lascannon and missile launcher for a dreadnought as a walking weapons platform, but now that we need heavy flamers, multimeltas, melta guns and a feircer concentration of tough units capable of close combat, the role of Dreadnoughts has quite dramatically changed -for the Space Marine Dreadnoughts at least. Ork Dreadnoughts were always stuck in a combat role and the Eldar Wraithlord was always incredibly versatile.
So sticking with having a 'versatile' unit, it's a tough choice between the standard Dreadnought with mulitmelta, close combat weapon, heavy flamer and extra armour at 130 points OR the Ironclad Dreadnougyht armed with close combat weapon, heavy flamer, seismic hammer, melta gun, extra armour, move through cover at 145 points.
One is an all-rounder, one is a close combat monster.
Both will tear apart a vehicle in close combat.
Both will decimate a squad in close combat (Ironclad gets +1 attack).
Both have extra armour so they can always move and charge.
Both have heavy flamers.
Both can take Drop Pods.
Both get destroyed by close range melta guns.
The Ironclad can 'move through cover'.
The Ironclad has armour 13.
The Dreadnought is marginally cheaper in points.
The Dreadnought has a multimelta for range 24" and 2D6 armour penetration at 12".
The Ironclad has a melta gun for range 12" and 2D6 armour penetration at 6".
Both Dreadnoughts are very closely matched. The Space Marine Dreadnought is better at offence due to its versatile nature and longer ranged weapons, meanwhile the Ironclad Dreadnought is better at defence as an objective guardian in your deployment zone due to the short range nature of its armament and its tougher armour.
If they both deployed from Drop Pods, the Ironclad would be more survivable against enemy retaliations, but may find that its melta gun is out or range compared to the Dreadnought's multi melta for when it comes to tank hunting.
It's only in the following turn that either Dreadnought may get into close combat, but if your opponent is daft enough to let you charge his tank, you need to find more experienced opponents!