There are a lot of different factors that could come into play between two different cues:
Do they have the same tips?
Is one shaft diameter different than the other?
Is the balance point on the cues the same distance from the butt or joint?
Is one cue heavier than the other?
Are the tapers different?
Are the joint materials different?
Two cues of the same length can have an identical overall weight, yet be totally different in construction, materials, and balance.
Two cues that are completely different in weight can have the same balance point (in matter of inches from the butt or joint).
Personally, I think I can draw the ball better with a heavier cue that is a bit more butt heavy. I played the majority of my life with a 14mm, 21 oz cue and I have drawn the cue ball two table lengths or more on a 9 foot table. That is 18 feet, or more. I don't think one should have to draw a cue ball much further than that too often.
Earlier today, before I read this, I was measuring the balance points on several of the cues I break out to play with. I think the balance of a cue matters more than the weight when it comes to doing some things. Differences in balance points can cause you to chase stroke lengths, bridge lengths, and stances which will affect how the cue ball reacts.
http://forums.azbilliards.com/showthread.php?t=437482