Hope nobody minds me necroing this post, but since I'd like to discuss what my personal favorite units are, and why, and since someone already made a thread about it, I might as well revive it, especially for the newer players to view it.
Anyways, my personal favorite unit right now, overall, would have to be the Phoenix. Why? Well, for starters, I prefer to start games with the Airplane Plant. Why? For 2 reasons. 1st, I believe that, due to their unrivaled speeds, and ability to traverse over any terrain, aircraft are not only the best option for covering vast distances, but they're also most often the best at performing raids, especially in the early game (when strong air defenses, like Artemis, are absent). Of the aircraft that perform this role, I personally find myself building Phoenixes the most. Why? The Phoenix is capable of carpet bombing groups of enemies with napalm bombs, which makes it the Airplane Plant's closest thing to a riot unit. (Although the Likho could drop far more powerful singularity bombs that can deal heavy damage across a wide area, and is quite tough on top of that, more often than not, I find the much cheaper Phoenixes to be more cost effective at bombarding groups of enemies.)
As for my favorite construction unit, that would be the Crane. Why? Well, that would be the 2nd reason why I typically start with the Airplane Plant, and that is because it's not only capable of traversing over any kind of terrain, but it's the single fastest construction unit in the game, able to quickly reach distant mexes (and other strategic points of interest), and the price is still fairly low. Sure, they have low buildpower, but my commander (plus some caretakers, and later, other factories' constructors) can typically fulfill my base-building and economic developmental needs.
As for my other favorite air units, I find myself preferring the use of Swifts over Raptors. While Raptors would most likely dominate Swifts in combat (on a per-cost basis), the Swifts are better at intercepting enemy bombers due to their superior speed and dps (also on a per-cost basis), and can engage ground units if need be. I also use Thunderbirds to disarm enemy ground forces in advance, to give my air forces (or ground forces) an opportunity to dispatch them in relative safety. Later on, I would add Nimbus gunships to my air force due to their ability to engage ground forces with their rapid-firing weapons from a safe distance away from anything that isn't an anti-air unit (essentially making it an airborne riot/skirmisher unit), and also due to them not needing to rearm using an airpad.
Of course, the enemy would most likely catch onto my strategy of focusing on air units for the early-game, which is why I'd need to build a new factory soon after the start of the match. Of these ground-based factories, I'd most likely want to build a Spider Factory. Why a Spider Factory? Because my favorite ground unit, the Venom, possesses the ability to paralyze small groups of enemies at a time, and is fast enough where it can even chase down some skirmishers. Moreover, in a 1-on-1 match against a Knight or a Blitz, both of which can also paralyze enemies, though over longer distances than a Venom, a single Venom stands a good chance of coming out on top of either of them, because it not only has enough health to avoid getting paralyzed from a single shot from a Knight or Blitz, but is also likely to get off a 2nd shot before either of them due to having a faster firing rate than them, and 2 shots from a Venom is enough to paralyze both a Knight and a Blitz.
Even though the Venom might be my favorite ground unit in the game, I do know that it needs support from other units, not only because it has trouble with enemy skirmishers (as riot units typically do), but also because it's simply lacking in the ability to put down enemies for good. Of course, it could rely upon Recluses or Redbacks to dispatch the enemies that the Venom has paralyzed, or masses of Fleas to swarm enemy skirmishers, but I believe that other factories have better units that I'd prefer to support my Venoms with (with the aforementioned Phoenixes being ideal replacements for the Fleas).
Not long after building a Spider factory, I'd want to build a Rover Assembly, so that I could support my Venoms with Fencers, which I'd consider my favorite Skirmishers due to their long range homing missiles, and Badgers, which I'd consider my favorite artillery units in the game, due to their low cost and ability to litter battlefields with mines that explode whenever enemy units get too close. Later, I'd want to build a Shieldbot Factory, so that I could swap out the Redbacks for Outlaws, which constantly emit an A.O.E. attack that also has the benefit of slowing enemy units, and add reasonably-cheap Racketeers to my ground forces to better help deal with enemy heavy units and striders (alongside my Widows, which can quickly paralyze said heavies and striders) thanks to their long-range disarming missiles, which should make it a bit safer for my remaining ground forces to close the distance, and finish off the enemy heavies or striders.
After that, I'd look into building a Jumpbot Factory, so that I could start adding Placeholders to help with clumping up enemy units, so that my Phoenixes, Nimbuses, Fencers, Badgers, Firewalkers, and later on, Crabs can capitalize on the enemy units' predicament (of getting themselves stuck in place due to the miniature black holes that the Placeholder launches). Eventually, I'd also want to use Anglers (from the Amphbot Factory) due to their comparatively high burst damage against aircraft (compared to any other ground-based AA unit), Lances so that I can snipe enemy units and structures, especially heavies and striders, from a safe distance, maybe the occasional Tremor to bombard bases or units from a long distance, and of course, the occasional Aspis and Iris to provide my ground forces with shielding and cloaking respectively.
Sadly, I don't have a particularly high opinion on not only striders in general, but heavy units in general. For starters, they're all just too expensive for my liking. For all the damage that they can dish out, most of them tend to overkill the smaller enemies, and for all the health that they might have, a determined player can quickly and painlessly take them down with help from cheaper anti-heavy units like Widows, Racketeers, Lances, Ravens, and (if the player is really desperate and short on cash) Snitches or Puppies to name a few. In fact, perhaps the only striders that I'd most likely want to build would be the Merlin and Scylla for their long-range fire support (and ability to shrug off a single bomb from a Likho), and the Funnelweb, which comes with a built-in area shield along with a complement of drones. Even then, it'd be until I have a sizeable economy that can support a large army of smaller, cheaper units.
