Internal vs. Extenal

I prefer an internal frame pack if I am going to be using it daily or for back packing. They just seem to be easier for me to fit comfortably. I think it is because I am a medium framed guy but very lean so I am prone to feel more of the rigid edges that won't conform to my build.
When it comes to hauling heavy loads like your talking about with meat and what not you just can't beat an external frame. They are the ticket for weight and will allow you to pack more weight comfortably than an internal frame because they stay rigid.
Hope that gives your some perspective.

I have both types and use the internal frame for a daily pack and to carry lighter loads. The external frame packs make it easier to carry heavier bulky stuff. You can adjust it higher or lower to suit the balance you need depending on the terrain you're in too. The higher it carries the load the easier it is to walk with lots of weight. I carry it lower when I need balance for rugged terrain but then it tires me more quickly.

I prefer the Molle II military for heavy meat loads. It actually works real well for an all around pack as well. It can stand a lot more load than I can carry.

if you want to use one for meat hauling than an external is the way to go. I can carry much more than would ever imagine on one of those compared to an internal. besides the weight is on your hips on not your shoulders as is common with the internals. This helps against fatigue and also helps when time to clean the pack after a haul gets a little messy. Externals are simple to clean where the mess is on the outside instead of on the inside of a pouch.