I agree that at 3.5 lbs it's no lightweight, but that's with those nice padded legs for soft ground, individual adjustable legs and the ability to swivel which might be nice if your setting around on a lookout looking for photo-ops.

That Helinox is nice and light, but as prouboy said, the feet sink into soft ground and I'm guessing you better set it up on fairly level ground or you could have problems ?

I checked, a tennis ball weighs between 2-2.5 oz.
The chair weighs 2 lbs, add say 4 x 2.oz tennis balls, and your pushing 3 lbs.
Don't know enough about either, but by just looking at pictures and what there made of, I would say the Shappell chair would probably take 
abuse better than the Helinox?

So I guess like everything involved in tripping you have to decide what's worth lugging and what's not. ;D