This is one of those games that developed my interest in military sci-fi, though the first of the series Aftermath was the one that actually sparked it off. Aftershock is a big brother/second attempt of the formula laid down by Aftermath and does very well. The only gripes of the time was Starforce which is now devoid in this DRM-free version, and there are various mods and modding guides if you feel the need to change the game.
There are factions, and it's a good idea to be friendly to at least the humans but a better idea to be friendly to them all. Humans are generic and my favorite as they get the best flexibility in the field, Cyborgs make excellent high-speed high-health tank-scouts, and Psionics are fine medics with decent sniping capability and a '6th sense' which can detect living creatures through walls. As I mentioned above just be friendly with the humans and you will be fine, they are flexible enough to be anything but an uber-tank. Resource and base management is done proper but I will give you a warning, you can't just grab a ton of bases and use them all. Supply lines through territories cost maintenance to keep going and the cost gets higher for more and more lines so be careful and thoughtful on which bases to attach and which ones to leave as-is. Building space in bases is limited also, which means capability to make advanced items and weapons will be exponentially more expensive. This forces the player to use 'cheap' equipment for a long while as a means to keep fighting, and to use common munitions for a long while. I would easily say the game is very balanced.
To cut to the chase, if you like Aftermath then Aftershock is a truly well-done sequel. If you haven't tried both, then it's the best infantry tactical game I ran into that is modern (XCom requires DOS and is dated) and there isn't many games to fill the niche Aftershock does, nor do they do it nearly as well.