Which is more Acceptable to God. Silent, Vocal, or Both Kinds of Prayer?

I never felt that life was right for me.  Part of the reason I felt cheated is because I attended Church my entire life, and yet I only got to be apart of a youth group for about one year.  I realize when I say "about one year" that tech. It was three years.  But the youth group I was apart of was pretty much worthless to me. 

The Church I attended couldn't keep youth pastors.  Every Youth Leader it ever had only lasted one year, and then you was onto the next one. 

The youth Pastoring was pathetic.  Most of the guys they got never went very deep in scripture.  Mostly it was just some kind of devotional booklet that taught some very elementary Biblical/Life lessons.  I think it's probably ok for younger kids, but for a 19 year old, who had been through deeper lessons, at his old Church, in the Fourth and Fifth grade.  This didn't cut mustard. 

While I was probably more learned then the younger kids in the group.  I wasn't spiritually mature enough to be some kind of leader.  At this point in my life was really really doubting my own salvation.  And at School, I was starting to get so sick of things, that I was experimenting with swear words.  A VERY CONFUSED TIME IN MY LIFE indeed.

For one year the extremely small youth group of about 3 to 5 people.  Had a decent youth leader who I could look up too, and share things with.  He had come into my life too late, in my opinion.  (I know your all thinking this must be the way God wanted things...  And maybe your right.   But it didn't make the experience feel any better back then, and it hasn't helped me feel any better now)

This youth leader was a little on the charismatic side.  Which I felt was a good thing because it made things a bit freer.  However with that came in some controversial ideas.  I'm not saying those ideas are wrong.  I just don't know if they are right or not. 

My parents taught me to pray both out loud and silently.  But my dad prefers to be pray silently.  So when we sit around the Kitchen table, to each our Sunday Dinner, Mom is usually the one who prays out loud for the food.  Once in a while for Fathers Day, Mothers Day, I'll do the praying out loud. 

I look back at this, and I noticed that when I was a young kid, I had no trouble praying out loud.  In fact back then my Mom and Dad would alternate.  But as He started to go more silent, so did I. 

For a long time silent praying seemed ok for me.  I was content to pray silently to myself.  Then my youth leader made a comment that Silent prayer is really a more recent thing people do.  But in Bible Times everyone prayed out loud.    I don't know if this is true or not.

I think for the most part, I just took a mental note what the youth leader said, but didn't put it into practice until more recent years.  (Almost 11 years later) 

For several years, I would go out my car early, and then I prayed out loud before I came home from work.  This fit me very well, because I felt like I was doing something that connected me to God, and it worked well into my time frame.   But things in my life have changed to the point where I can't do it this way anymore.  (I'm not telling you that I can't ever get it worked in.  Once in a blue moon I can!) 

Thank you for reading this long thing.  lol  Now it's time for my question.  I would like to know, How we as Christians come to the conclusion that silent prayer is the way we should pray?   Is silent prayer as effective as prayers prayed out loud?  How do we know which or both is acceptable to God?  Could the method of praying be more acceptable for one person and not as acceptable for another?  (After all prayer is a personal communication between you and God).  What do you guys think?