I run a full Marksman primarily, with 7 points in Ranger for Eagle Eye(5/5), Killing Focus(2/2) and the root ability Predatory Instinct, and 8 points in Nightblade for Blazing Fury(5/5), Coup de Grace(3/5), and this gives me a stealth and 20meter sap for 45 seconds which is just a bonus as I chose these secondary souls for the damage. I've seen and tried other variations of full Marksman and thus far found this one very much to my liking. The Marksman will also be getting buffed in v1.2, as it relies heavily on cooldowns for the big damage.
As far as stats go, that usually takes pretty good care of itself by just going with the upgrades. Some people stack physical crit, which can be rewarding, but as I am not a very lucky guy I try not to rely completely on chance for my damage, though just by going with the upgrades I am quite happy with my crit percentage. If I am unsure of which item is better I use a point system which makes it quick and easy:
Breaking it down the point system is based around dexterity and how your stats are affected by dexterity. 1 Dex = .5 attack power and 1 physical crit. So I figure .5 attack power must be about as good as 1 physical crit, as they are both vital for dexterity souls. And because I rather work in whole numbers than fractions I make .5 attack power = 1 point, and 1 physical crit = 1 point. Now with that basic idea this is how I rate stats --
+1 Strength = 1 point (each point of strength gives .5 attack power)
+1 Dexterity = 2 points (gives .5 attack power and 1 physical crit)
+1 Attack Power = 2 points
+1 Physical Crit = 1 point
I have also observed that two items of equal worth, one centering on attack power, and another on physical crit. The attack power item will generally have half as much bonus to attack power as the physical crit item to physical crit. This is another reason that has lead me to believe .5 attack power is essentially equal to 1 physical crit in the general sense.
It is different between souls which is more important. And with some you can go either way. It is really something for you to decide, but if you aren't sure then just go with the item with the larger point value. :)
(I hope that was understandable and helpful hah)