Agility gives you access to athletics and Weapon mastery.
Points spent in athletics let you move faster, however the more armour you have on you the slower you will move.
Weapon mastery gives you weapon proficiency points that you can spend to swing a weapon faster. Weapon master is a diminishing return. The more points you put in the less and less weapon proficiency you get back out. Most people swear by 130 in melee weapons.
So in summary agility is very good but up to a point, agility suffers from diminishing returns. Pumping agility used to be very popular before the big patch that introduced the diminishing returns. Most people swear by 5 agility.
Strength gives you access to Iron Flesh and Power strike.
Iron Flesh gives you 2 hit points per point spent, does not sound like much but the higher the armour the longer these extra points will last you. My thoughts are go all the way with Iron Flesh or not at all, a couple of points are not going to help you out that much so spend them elsewhere. But if you are looking to spend 6 points and up IF is a good bet.
Power Strike lets you hit harder. This is a must otherwise might as well roll up a towel and flick it at people. Most people swear by at least 4.
So in summary strength does not suffer from diminishing returns hence the argument that str is better.
Overall
You need both agil and str. You need agility for weapon master and to move in and out of danger and you need Str for at least Power strike. I would suggest a minimum of 12 strength for any build, but that is the bare bones minimum and you will glance off peoples armour with that.
What's the minimum for agility? Well you could go with 3 but in tin can armour you will be slow real slow. Myself I prefer a minimum of 9, but that is me.
What are some common builds for agil and str (Converted over 2 points)?
Strength/Agility
9/27 --->Ninja High Agility type build --> Very fast paper tiger, a stiff breez could kill you.
15/21 -->Fast Build --> I like this build so so hiting power but the extra agility moves you in and out of danger real nice.
18/18 -->Balance Build --> Its a good standard build.
21/15 -->Strength Build --> Nice build, but your timing has to be a bit better since you are slower, fighting good high agility people with this build is a pain.
24/12 -->Heavy Str Build
27/9 --> Very Heavy Str Build goes great with high quality armour, the IF are magnified by the armour. But you are slow, damm so slow, my grandma could outrace you.
Conclusiong
Agility and strength are both good, you have to know your play style and what you prefer. A quick guide:
If you are a very good blocker and have excellent timing, I would say pump agility as much as possible the extra speed will make you all the more deadlier.
If you have decent blocking and decent timing a fast build might work well for you.
If your blocking is so so, and your timing is not all that great go with the balance build the extra agility will help you move in and out of danger and compensate for average blocking skills and poor timing and you will still have decent killing power.
If you have decent blocking skills and you have decent timing an Str build would work well. A bit slower so your timing has to be a bit better.
If you have very good blocking skills and good timing a high str build will work well for you. BUT if you have really bad at blocking and have really bad timing a high str build will also work for you PROVIDED you throw a crap load of armour on and get a long spamming weapon like a Poleaxe or Great Long axe.
Cheers,
Formless