all comments based on the FH system
trying to compare wich is better is going to be very hard, as it comes down to personal preference. if what is being played by the PC's right now is any way of telling, damage after a set amount of time is the preference right now.
however certain factors can throw off the entire debate, skills, resists, immunities, other forms of combat, etc.
even if you had a monster that swung death and had 5 million soak, he could still be killed in one hit in the FH system.
the main difference i see personally between the two is surprise and illusion of damage, the rouge has both. base damage can not go higher than 5 ever in this system. so if you do manage to swing that amount, only the weakest 0 level character ever is going to go down in one hit without time to react and run, fight, etc.
however with damage after a set amount of time you may not be doing as much damage over time as base damage, but your damage dealt in one hit will be high, thus the illusion of damage. this also provides the chance the your opponent will not have enough health to take the hit, and therefore not react, surprise.
the following are unassisted damages, no items, potion, spells, etc. . . i belive
as well as skill points required to purchase, also overlooked i feel
highest damage over time
melee - 15 damage over 20 seconds - 200 points
ranged - 33 magic over 60 seconds - 150 points
ranged 2 - 10 vorpal 55 seconds - 90
highest base damage
single weapon - 4 - 240 points
duel weild - 2 - - 150
crush single weapon - 3 - 240
vorpal single weapon - 3 - 240