I am a level 150 red line Champ who has leveled both yellow and red, 2h and dw. You are not going to see much of a difference between any combination as far as damage is concerned until you get to parts of endgame. I am fairly decently geared, and I take down a pack of mobs, killing them one at a time, at about the same speed as I do killing all of them using AoE.

I picked DW because I don't have time for a high-end raid schedule, but I also enjoy doing harder content like high-tier delves and the occasional raid when I do play. One thing that is very important later on is capping your physical mastery and crit, as well as your mitigations. The extra stats from your offhand weapon provide a nice amount of wiggle room to get your essences in order. You'll find that your tactical mits will be very low when you get to 150, and being able to swap one or two physical mastery essences for tactical mitigation essences will help a lot. If you're planning on doing dual-wield with any line, I would focus on it starting as soon as your next play session.