Vanilla Marines: Ryu
Strengths: Jack of all trades.
Weakness: Master of none.

Vanilla marines are a versatile force, with plentiful access to good armour, cheap APC's, as well as solid anti-tank solutions, powerful HQ choices, etc, etc... They cover all the bases.
Just like Ryu - he can cover close to medium range comba with an array of moves, has a devastating "anti-tank" move in the form of his Dragon Punch, as well as solid ranged attacks with his hadoken and shinkuhadoken.


Blood Angels: Ken
Strengths: Like a more aggressive Ryu.
Weakness: Slightly less knock-down, drag out power.

Blood Angels are the marine equivelant of snooker balls in a sock. Just like Ken, they excel at fast, relentless assault, but have slightly different defense, meaning they play best when attacking. Like Ken, they aren't weaker than Ryu/Marines - they just play better at close-ranged assault.


Space Wolves: Sakura

Strengths: Quirky, effective tricks.
Weakness: Quirky moves leave you open to clever exploits from superior players.

Sakura looks like she plays like Ken or Ryu. She doesn't. Her moves are only very superficially similar, and she does a lot of things very differently, which will catch an opponent unawares. Her Dragon Punch isn't as directly powerful as Ryu's, but it makes up for that because when it does connect, my word do you know about it. Just like the Wolves; they don't play the longer range fighting as well, but the sheer number of short range special weapons brings a lot of pain. Players who come expecting just another 3+ army/Ryu will be easily caught out. Those who know what they're doing will have a hard fight, but a winnable one.


Grey Knights: Shin Akuma

Strengths: Merciless, relentless onslaught of powerful combos; terrifying in the hands of a master.
Weakness: Vulnerabilities do exist, but they are not immediately obvious, and require forethough to spot and counter.

Shin Akuma is terrifying. Nine times out of ten, he steps up and demands you hand over your face. He has outrageously overpowered moves, like the aerial fireball and the Shungokusatsu, which are extraordinarily difficult to counter, as well as high-damage. Sound familiar?
However, he does have vulnerabilities - as do the Grey Knights. Their lack of 3+ invulnerable saves, their 24" maximum range, their general low model count all count against them - yes, their high power level compensates for this (and then some!), but they can be beaten by a canny player who builds a list around those weaknesses.


Dark Eldar: Hugo

Strengths: Astonishingly high attack power and speed.
Weaknesses: Make a single mistake and die. High skill level needed; not a pick-up-and-play option.

With the right moves, Hugo can move like lightning, and if you know what you're doing, you can crush an opponent in moments with some devastatingly vicious attacks (I say this as a man who favours street fighter 3: third strike Hugo as an extremely powerful character, and who uses him to routinely beat Ryu and Ken players). He plays much like the Dark Eldar, because he is unforgiving of mistakes - if you slip up, you can rest assured that you will be on the end of a much bigger string of hits than an equivelant option.


Necrons: Urien

Strengths: Survivability. High attack power. Good mix of ranges.
Weaknesses: Some moves leave you very vulnerable to counterattack. High skill level needed; not a pick-up-and-play option.


Urien is a boss. Literally in the case of street fighter 3. He's slow and purposeful, but hits like a truck, and has a number of clever trick moves that let him overcome his normally slower-than-average pace. Again, seeing the connection? The Necrons bring the pain in a totally different way to Marines, and that is true here - play Urien like Ryu, and you'll just die every time. Play Urien like Urien and you too will be a boss. Play Necrons like they're Necrons, rather than Marines with a 4+ save and "weaker" FNP where each unit is a little army unto itself, and you'll lose. Urien's moves call for a lot of synergy with each other. His Aegis Reflector is a terrible move on it's own. Combo it with other moves and suddenly it's a recipe for instant death. Necron units work this way too. Scarabs on their own? Not so good. Combined with Tomb Spiders, and suddenly much more threatening. Combine with supressing Gauss fire, and suddenly those AV14 tanks aren't going to make it to turn 3.


Tau: Twelve

Strengths: Lots of weird little tricks.
Weaknesses: Low attack power, made of tissue paper, ranged game looks good on paper is actually terrible, weak up close. Basically, made of frustration, no matter how cool it looks.

Yeah, I think I've covered the Tau there.


Tyranids: Alex

Strengths: Unexpected weird stuff other options just can't do. Attack spam.
Weaknesses: Underpowered on all levels compared to other options.

Tyranids should be awesome. Like Alex; he looks cool, he's a main character, yet doesn't have a single move in commomn with Ken or Ryu. He's just... well, underpowered. I mean, he's not rubbish; you can win with him. It's just a massive slog compared to other options, and the wins never feel quite as satisfying as they do with another, more awkward-to-use character like Hugo, because there's never that risk of truly death-or-glory dramatic failure or dramatic success. On paper, Tyranids should be awesome; they should be like the Dark Eldar, and play in weird, powerful ways. But everything's toughness 4 with crap armour, and so their attack power counts for very little. All those weird tricks? You'll want to use them, but stop when you realise they're just not as effective as you feel they should be.