TOPIC: Size Does Matter!

The different sizes are for different applications. The dreadnaught was designed in the early 30's for the purpose of volume. They wanted to compete with banjos and fiddles. That's also why the dread is the guitar of choice for bluegrassers. The OM's 000's, 00's and such are, some say, sweeter, not as "boomy" in the low end and more balanced which is desireable for fingerpicking.
The whole thing is subjective, though. I've found when looking for a guitar, play what you normally do, play as many guitars as you can find and the "one" will find you. Just be aware that that one might be a more expensive model than you planned on. I like dreads, personally, but I prefer to play standing up so it's much easier that way.
I also own a Martin "M" style guitar which is also called a 0000. It is the size of a jumbo but the depth of an OM, like the Mayer. It feels like a small guitar but can deliver the tone and sound similar to a dread.
There's just so many kinds you can try new guitars for years and keep finding different things you like and dislike. And that, my friend, is a great way to have fun.

I notice right away when i use a different axe it takes a little getting use to becouse i am use to your guitar, especialy when you use a youth size tha has a shorter neck and has less frets.

I don't know if this is the right spot for this comment, but when everyone is talking about the sound coming out of their guitar, I have noticed one thing that really affects the sound, and that's the pick being used. I've played my guitar with Silvia's pick, a fairly solid firm one, and then back to my very flexible pick, and the sound is totally different. I prefer the more flexible pick at this point, which is I'm still trying to get comfortable with using a pick instead of fingering.

SAM!!!!! You are using my PICK?????? NOOOO!!! I bought you your own stash.....stay away from my picks...

The soft pick is alot easier to control, but the attack on the strings is somewhat softer, and so the volume isn't as loud. I use a medium gauge pick, it seems to be a good compromise. The soft pick is great for strumming, and is alot more forgiving if you have alittle too much pick projected out, it won't "hang up" in the strings, it seems to glide better when strumming. This could be a crutch for poor pick control, so i'm trying to train myself with the medium gauge ones to learn better pick control.

I recently started using a heavier gauge pick. When I first started playing I would only use medium or light guage picks. They were easier to controll like Dave just said. I've found now though that even though they are less forgiving, it's helping my right hand technic and I like the better sound projection.