IMHO there is not enough info provided to make a accurate decision. We need to know if you pack light or heavy. Do you eat noodles, or do you pack a Coleman 2 burner stove with you. Do you plan on using a tarp or tent? How much ground do you plan on covering? There are a lot of variables that will affect you dramatically if you don't pick the proper gear.
Personally, I have 4 bags, all of which serve different purposes.
1) "Personals" bag which is nothing more than a Frost River satchel bag, or "murse". I keep the basics in it and carry it when walking around on the property or taking a little walk in the woods.
2) Camelbak HAWG is my day hike/geocache/carry-on bag. For the most part I keep the basics in it plus some snacks, water, tp, and anything that the family may need.
3) Camelbak Motherlode (older version) is my tarp and/or warm weather overnight bag. I have finally figured out what I need and what I don't need when it comes to staying in the woods overnight. I can use this bag when I am packing light as it does have a waist belt of sort and is comfortable and big enough to use for a overnighter.
4) Kifaru Zulu is going to be my tent and cold weather bag (I haven't had the chance to use it yet). This pack isn't huge but I feel that it is big enough to handle my gear when expanded out, but can be cinched down fairly small for when I have a lighter load.
Now I am not saying that you need multiple bags right off the bat, I am just saying that you need to determine how you will really be using it, and what you will be putting in it. If I could only have one bag right now, I would opt for the bigger bag because it will handle the loads better. With that being said, in my humble opinion, there are better options out there for the money.
Here's an option.
http://www.campmor.com/outdoor/gear/Product___90288