Dual hand weapons, such as Rykuta's "L4D pack", are meant for realistic, FPS style BL. Weapons such as Bushido's "Tier and Tactical" are meant for 3rd person, multi-use, a bit unrealistic style, a bit more like playing with legos than turning on an Xbox and playing Call of Duty.
It's a matter of personal prefrence, and also what you're wanting to use, such as hosting a "Tacticle Training Facility" server, you would want First person style guns.