Here's my opinion on the Summit stands that you listed (hopefully this won't p*ss off anyone! [:-] )
Summit Viper Classic: Heavy gauge steel version of the Viper X4. Same stand. Same look. Same everything. Just weighs a bloody ton more than the X4. Do this: Go to a store where they have all the Summit stands already boxed up for sale (Dick's Sporting Goods, Galyan's, etc...) Pick up the Summit Viper Classic. Reach down and grab the whole box and lift it up. Notice how heavy it is? Imagine hiking in 1 - 1 1/2 miles with that weight on your back! [&:]
Summit Viper X4: Lightweight aircraft aluminum version of the Viper Classic. Surprisingly light and rugged for the size of it. I mean,
amazingly light. After picking up the box with the Viper Classic in it, you go and pick up a box with a Viper X4 in it, and you will go, "Daaay-um! This weighs next to nothing!"
Summit Bushmaster: Another incredibly lightweight aluminum climber with an open front, like the Summit Broadhead Backpacker. The difference here is the Bushmaster doesn't have a backrest (highback seating cushion), and it doesn't fold flat like both the Broadhead Backpacker and Bullet Backpacker. It's nice, but then, once you sit in a Viper or Goliath or Cobra, with the highback cushion, you won't look back).
Summit Broadhead/Bullet Backpacker: Really new, really cool, stands that fold flat as a dime. The Bullet Backpacker is essentially a Viper X4 but the big "V" brace in the back collapses down to fold flat. The Broadhead Backpacker is essentially a Bushmaster, but with a backrest, and it too folds flat. Believe me, I
really studied the Summit stands and did my homework. I tried them out and various stores and at a big sportsman's show that was here in town a few months ago. I liked the idea of the flat folding stands, but then, at the last minute, I changed my mind, because of the possibility of it making noise while assembling it in the early hours before climbing the tree.
Long story short: I got a Summit Viper X4 and absolutely LOVE IT!!
At 6 foot, 205 lbs, and 43 years old, the Viper X4 easily holds me securely and allows me to easily climb up a tree without worry.
Hope this helps answer some of your questions!
Butch A.