The only way to know is through repeated practice and competition using one or the other.
For me personally, I prefer to have the cue along my chest when down on the shot.
The biggest benefit is it forces you to stroke straight. Obviously you can still twist your wrist which can pull the cue off line, so it's not a be all and end all to a straight stroke.
The other thing you need to look out for, which plagued me when I first started, is not having the cue too tight along the chest. If it's too tight, you will have a tendency to pull off line on your backswing.
The trick here is to bring your chest to the cue, and not the other way around.
Larry,
As are some other parts, the bolded part of Jon's post is obviously true, unless you changed your mind when down on a shot & raised the butt end for a specific reason.
The cue
at times touches my chest too. As I have said in one of the PMs, it is the position of the balls on the table & the line of the shot that can
at times put one in a different position than 'normal'. Still being able to stroke straight at those times is what can separate one level from another.
I don't think it matters that much which method one uses as long as it is best, for YOU. Like Jon said, I don't think anyone can tell you which would be best for YOU. You have to find out for yourself or perhaps with the help of a 'knowing eye' like Frans.
Also, I don't think I quite agree with the statement by Jon that it
'forces' one to stroke straight, but it can be a source of immediate feedback & I would think much more so if it is one's primary method.
Touching my chest is not the norm for me but when it is doing so for the shot at hand, I don't usually mind if it leaves my chest as the cue would be traveling on a more flat plane & I know that I can deliver it back to where I want when that happens.
I think I'm getting too much into some specifics.
Anyway, I certainly don't see the cue touching & staying in contact with the chest as a bad thing, especially if the contact 'pressure' remains constant, as that would be an indication to me that the cue is not 'rocking' as in some other strokes That is unless the body is also moving. I like it 'straight away', into & through.
We all need to keep in mind that we all are not using the same exact type of stroke.
Like Jon said, test it out for yourself. Shoot every shot that you can with the cue constantly touching your chest with a constant 'pressure' & see if the results are better, the same, or not so good.
I'd then suggest going back to shooting without it touching the chest for an immediate comparison.
You may find that one or the other might require a slightly different connection to the cue in order to do it consistently without an associated change in something else. One thing may lead to a better other thing.
Like I suggested in the other post, focus on the straight stroke & let your body form around it so it puts no outside influence on that stroke. I think some call that a free flowing stroke.
Good Luck with the experiment & Best Wishes,
Rick