The trident is better for soloing, but the dagger will give much more dps, BUT the dmg difference isn't that noticeable until your rogue is in his 80-90's and has enough strength to maximize the dagger. So, I would recommend using a trident until you get to 80-90's and then you can try and trade it ...
The entire reason one would use a spear build to effectiveness is to spam skills. My alt can 2-3 hit mobs my lv with an onyx spear and golden trident. Pretty much quick lving spam 2 skills in a row or use skill then wait for auto to come behind it.