Here is another edition of How to Build an Ork Army from Culler:
-Battlewagons are best used as transports. Battlewagons with killkannons are expensive for what they do, but then again the Ork army lacks low AP weaponry, so you’re paying a premium for a rare ability. It’s easy to put too many upgrades onto a battlewagon, so choose its role carefully and gear towards that. There are plenty of battlewagon tacticas floating about though.
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-Looted wagons make decent transports in a pinch but I don’t recommend it. Looted wagons with a boomgun and ‘ard case are pretty decent for providing low ap large blasts, but only if you’ve got other vehicles because if they’re alone they will just get quickly destroyed. They’re still probably high priority to kill for most opponents. Compare a looted wagon to a leman russ and you get an idea of how much you're paying for how little as an Ork.
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-Killa Kans are pretty amazing, one of the underdogs of the Ork codex that most people write off. They’re incredibly cheap and for their points are extremely tough. The grotzooka is an amazing weapon for killing infantry and light vehicles and with their bs of 3 their other weapons have a decent chance of hitting too. Kustom mega-blastas are a little too pricey to be worth it though. A squad of 3 gets 9 str 10 power attacks on the charge too. Sure they’ve only got a ws of 2 but they still hit ws 4 troops on a 4+, same as dreadnoughts or deff dreads. Keep them lean, there really aren't any upgrades worth giving them since their cost is so low to start with.
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-Deff dreads are a suboptimal choice and generally not worth taking over killa kans, IMO. Their ranged ability is laughable until they get within template range, at which point a deff dread becomes about as effective as a pair of grotzooka kans are from 18” away. 2 AV 11 vehicles are tougher than 1 AV 12 vehicle too. The kans get more attacks than a deff dread unless it takes 2 DCCWs, at which point the kans outclass it at range completely and still have the same number of attacks on the charge. They both hit on the same number against ws 4 stuff and that’s most of what they’ll be fighting in any combat that’s not going to be utterly one-sided anyway. If your heavy support choices are full and you’ve got a big mek it may be worth taking a deff dread as a troops choice but not usually.
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-Flash Gitz are another suboptimal choice and usually not worth taking when compared to other units. Too many points for too little output that’s unreliable anyway. Flash gitz have the stats of 'eavy armor nobs with a better ranged attack, no extra ccw, and no options for upgrades like powerklaws. They're not very good fire support for their points and not a very good melee option for their points, but they can do both roles to some degree. If you want to use them take a painboy and/or put them in a battlewagon. The more dakka and shootier upgrades are both good if you do take them though. However, you're much better off getting your anti-infantry firepower elsewhere. For 30 points you could have either a flash git with 2 str 5 shots with 24” range and bs 2 or you could have a warbuggy with 3 str 5 shots that are twin-linked at 36” range. You're basically paying a premium for nobs that sacrifice some cc ability to get a lackluster ranged option.
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-Big Gunz are decent ranged support, especially kannons. Zzap guns are too unreliable for killing tank (average penetration strength is 10.5 to kannon shells that are average penetration strength 11.5 and are cheaper) and zzap guns are also expensive to be shooting at even the most heavily armored infantry. Big Gunz are also fragile, even a single heavy bolter has a good chance of killing crew and forcing them to run or wrecking the gun. They do ranged support well though, something Orks generally lack. Most people consider them too fragile to be relied upon and I’m inclined to agree. Generally deffkoptas or warbuggies do the tank hunting thing better.
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WAAAAAAAGH!