The upside: marvellously strange and unpredictable battles. There are fewer bread-and-butter tanks, planes and boats all told, but it's going to take you quite a while to try out all the different wacky stuff. The downside is that it is a lot simpler. On the most basic level, it's a real-time strategy game in which you can build a load of robots, lob 'em at the other guy and see what happens. Seasoned players will still skin you alive, don't doubt that, but so long as you've mastered the basics of resource collection you'll still present some sort of a challenge to them. This is about as close as RTS gets to button-mashing in a fighting game.
Whether the trade-off is worth it is going to depend on what type of strategy gamer you are. If your idea of fun is something that always pushes you hard, you may well find this too cuddly when compared to the first game, and especially against that other RTS I said I wouldn't mention again. If, though, it's about having an ad-hoc brainwave and finding a way to make it work, you're in for a much better time than the machine-cold first Supreme Commander offered.
When I play, I tend to concentrate on buffing up my aircraft as far as they'll go, so a fleet of them can shrug off the worst if they come into contact with anti-aircraft units or turrets and thus can deal incredible damage to even the most heavily-defended base. That's just me, though. One person I played against built almost no units, instead pouring everything into research, unlocking nukes incredibly quickly as a result, and promptly wiping my base and Commander off the face of whatever planet we were on before I'd got my first strike out the gate. I think it's telling that my response to this was not the puffed-out cheeks, clenched fists and made-up swearing that a too-quick defeat in other RTSes tends to incite, but rather to laugh. Well done, sir. That was an absurd risk you took, but it bloody well worked.
Another chap, meanwhile, busied himself with unlocking and constructing an Experimental Loyalty Gun, meaning that phalanx of suited-and-booted aircraft I mentioned earlier promptly and automatically converted to his side when they reached his base. All gone. All. Gone. I didn't laugh that time, I'll admit. The net result of all these steroidal sci-fi toys is that games tend to be over a lot more quickly, reaching sudden and wonderfully absurd conclusions when you least expect them. It's a different animal, and it is unquestionably going to annoy a lot of people as a result, but I honestly feel the many sacrifices made are worth it to experience this maniacal, ever-changing glee.
I realise I haven't yet mentioned something very, very important. All that fun stuff I've just been talking about? It only applies to multiplayer, and to a much lesser extent, the player-versus-AI Skirmish mode. Supreme Commander 2, alas, is a pretty awful single-player game. Granted, Supreme Commander and Forged Alliance came up pretty short in that regard too, but this is a whole new echelon of suffering. The missions are stilted affairs, cruelly built around denying you access to all the tech tree's wonders, and bookended with irredeemably grating and lifeless cut-scenes.
What a shame it didn't take a campaign map approach - a sandbox of territories the three factions war over, rather than a tiresome linear stomp. The idea is that it's an intimate tale, a look at this three-way far-future war from Just This Guy's perspective and how his family is affected by it. But hateful characters, lousy humour and a soporific pace ruin this. This sounds like an awful sweeping generalisation, but honestly you'd be much better off to ignore the campaign entirely and jump straight to Skirmish or multiplayer. That effectively makes this half a game, which means I've been doing a little panicky dance about whether I should score it lower than I have, but ultimately the multiplayer is good enough to redeem it. Well, if that sort of multiplayer sounds appealing to you.
This will split the Supreme Commander 2 fanbase in two. The game's made enormous compromises, but it's also brought in a superb sense of mayhem and variety. On the one hand it's a shame that it's going to leave much of its intended fanbase cold, but on the other there's nothing especially wrong with the first game, so stick with that if you don't like the sound of this. It hasn't aged particularly, and no-one else has stolen its thunder yet. There is absolutely no reason why it and its sequel can't co-exist, providing two related but critically different strategy flavours. Supreme Commander 2, after all, is an RTS about choice - that might as well apply to the game itself too.