Which Affinity is for me?

Dagos
Dagos Faction Skills focuses on AoE and Support type skills.  Dagos in general is more of a defensive and support affinity focusing on defense, critstrike rate and bonus, and resistances.  They have some AoE skills too, but the defensive and support skills are mostly what Dagos is about.  They also have those Potions that give Attack and Defense (+ HP restoration) and Resistances (+ SP Restoration).  So you are looking at 20% attack and defense + 100% HP restoration at 10.

In my opinion, Dagos should be a Balo's primary choice for affinity.  The reason I say this is because when it comes end game time, what skill will you be spamming the most?  I imagine you went the Powerful Aid route and you would have the charm making its cooldown 2 seconds which means its a spammable skill.

The Affinity Skills from Felkin just don't seem any good as I can put the same status effects on the other player and spam it like no other.  If you want to play the "bleed" game with the felkin skills, you can but there are so many factors to consider when  it comes to health reduction.  If you are a cash shop player who has all the $ in the world, then I guess felkin may be the superior one, but even then, Dagos is better.

Fuwa's skills are actually really good when compared to Felkin, but in the end, I see myself saying I will just spam Powerful Aid all the time.  This may be different for you.  Penetrator II is a amazing skill along with the other one.  The passive SP skill makes it so you are better tank than the other 2 affinities.

Dagos faction skills are just good because not only are they aoe, but they have a 30 second cooldown and will remove the target's spirit and buffs (Thunberbolt II and Song of Antipathy II).  Warsong II will increase your critstrike rate and skill accuracy which you will need.  The other skills I don't find any good and will be the last thing I would max.

The AoE skills would be good for AoE leveling except that you would have to gather the monsters first.   The Dagos AoE affinity skills are for PvP mainly.

Lastly, the ascension skills for Balo already make me say I don't need to go Felkin or Fuwa despite their cooldown.

To sum it up, Dagos Balos will have higher resistances, critstrike rate and bonus, attack and defense than the other two affinities.

Felkin
I don't have much to say about Felkin because I do not like any of their skills.

The Felkin Faction skills suck in my opinion.  One of my main gripes with them are their cooldowns.  Sure, Ordeal II is 12 seconds and removes the target's movement buffs, but the rest have a minute or more cooldown.  The Fuwa skills are mainly 30 seconds which means as far as single targeting, Fuwa would be more effective in my opinion unless the "bleed" effects from the Faction Felkin skills are really that good.  Once again, it depends on the player.

Fuwa
I like fuwa and actually it was a tough choice when I ascended on choosing between Dagos and Fuwa.  All of Fuwa's faction skills are great!  You should max them all as they are all VERY USEFUL in PvE and PvP.

As far as Fuwa Affinity Skills go, I don't really like most of them besides the "bleed" skills.  Bodhi Works seems pretty nice along with Moshu Disaster.  The Pet skills are always nice.  You would think Fuwa would focus on permanent resistances for your character, but Dagos actually focuses on that.  True Conversion is the only skill that focuses on any type of permanent resistance.

Any Balo who is a Fuwa will have the most HP/SP a Balo can have.  The only other thing is that it will be hard for a Fuwa Balo to come up with a good build compared to the other two.  This is because you NEED Powerful Aid and not Durable Fighter if you plan on having any kind of DPS in general.  The other issue is you have to max out most of your faction affinity skills compared to dagos.

Conclusion
In the end, if you want to be truely effective, you will need to have powerful aid maxed and have the charm to make it a 2 second cooldown.  After that, it is up to you on how you use your affinity skills as all 3 affinities can be effective.