Houses

The three houses differ greatly in gameplay - a definite plus. This is one of those games where people will endlessly debate as to which faction is the strongest. Here's a quick rundown on each house.

Atreides

House Atreides requires more micromanagement than House Harkonnen or House Ordos. Mobile Repair units love to be in the frontline of a battle if you group them with your attacking units. Sonic Tanks will decimate your own forces if they're in the middle of the pack. Kindjal infantry need to be deployed before they can use their rocket launchers. All of this adds up to a lot of hotkey teams and micromanaging battles. You need to make sure the Repair Vehicles lag behind while the Sonic Tanks lead the battle (which is a pain because they're slow), and you need to deploy/undeploy Kindjal every time you get into a fight. I don't like heavy micromanagement in battles (hardcore RTS guys would say I like to play a macro rather than a micro game).

Fighting for Spice

Looking for a target

Atreides attacking

Balance-wise House Atreides suffers from too many useless units. The Sand Bike and Mongoose are too lightly armored to put up a fight, and the APC is too slow in loading/unloading units. Sonic Tanks can wreck havoc, but they take a lot of tech building before you can get them and you'll inevitably destroy your own troops with them. The Minotaurus make up a little for the useless units since they have a lot of hit points, their guns are good against infantry/buildings, and they can take out vehicles easily if they're in packs.

The House advantage that allows Elite soldiers to train new soldiers in the barracks so they are experience right away isn't as useful as it sounds. Like I said before, it's damn near impossible to get Elite units in the first place (unless the computer gives them to you at the beginning of a mission).

Pushing with Minotaurus

Mopping up

NIABs tearing it up

Harkonnen

Harkonnen units have more hit points than Ordos or Atreides units, and they also have stronger weapons. Units like the Buzzsaw and the Flame Tank tear through infantry so efficiently that there's no point sending in footmen against them. The tank units destroy vehicles rapidly, and the Gunship and ADP are the strongest air units in the game (the Ordos Eye In the Sky is more of a floating bomb than an air unit). I think that House Harkonnen has the best balance between units; that is every unit has a place in battle, and a thorough fight will see every Harkonnen unit pop up.

The big disadvantage to playing as House Harkonnen is that it's the only house that can't repair units. Once a unit has taken damage, you can never fix it. This means that you can forget about getting Elite units and you'll have to spend more money on building units than the other houses.

Ordos

House Ordos requires a lot more finesse than Atreides or Harkonnen. The big advantage of using Ordos units is that they regenerate hitpoints on their own (much like Starcraft's Zerg). Ordos also has suicide units that are great for taking out buildings. The Eye In The Sky - an aircraft that explodes for damage and drops a suicide bomber for added insult -- can decimate a base in a snap. An obvious tactic is to destroy an enemy factory so they can't build new buildings, and then slowly pick off the rest of the buildings one by one - classic RA strategy.

Harkonnen forces

An Ordos base

Fighting for Spice

House Ordos isn't good at destroying infantry, however. Almost all of its tank units are hovercraft, so they can't run over infantry. The only artillery unit, the Kobra, is slow and needs to be deployed (so it can't move) for full effectiveness. The only units that are good at fighting infantry are the Gas Troopers, but since they're the lowest level infantry they die easily against even modest opposition.