doggie pack for training

[rosegoats2]

I'm new to goat packing. I got a couple of kids this spring. We've been doing short walks in the woods and the lead pretty well following right behind me.
I'm looking to take the next step and start getting the use to wearing a pack by starting with an empty doggie pack.
What doggie packs have folks had the best luck with or like the best?
Any thoughts about either of these?
http://www.rei.com/product/832677/rei-ul...s#specsTab
http://www.rei.com/product/855788/ruffwe...h-dog-pack