If you build a link that is adjustable on the vehicle with out removing then it can can unscrew itself and eventually fall out, more than likely it will just unscrew and will mess with the setting you were originally going for. Its not like your constantly dialing in pinion angle. So you set it once and then you don't have to mess with it, and you don't have to worry about it unscrewing itself. Dual threaded ends give you more flex and more adjust ability. I think if you asked clayton why it was not a left and right they would tell you its not a good idea which I agree with. They actually think about their designs and products from a performance and durability standpoint, not an ease of install exactly. Basically 80% of what they sell is weld on install, mainly b/c if your going to build something strong enough it really needs to be welded on to hold up. This is a short arm kit so much of the design element is limited but their long arm kit geometry and design I believe surpasses other kits on the market.
Square is stronger than round and as said all their stuff is lifetime warranty and square is their trademark. I personally believe they make the strongest suspensions on the market and they are not cheap but its what I have on my WJ b/c I wanted something to abuse that would hold up.
They saw our jeep out one time and he saw a bent link on my WJ. Sent me an email on monday asking if he could send me a new arm I never even spoke to them about it.
Now on the other hand we get Jeeps in here all the time with worn out joints, call X manufacture for a joint rebuild kit or new bushing. Answer: we don't support that anymore new control arms are X. But the kit is only 2 years old......... You get what you pay for. If clayton is overpriced Ill keep paying b/c every time I call them they know exactly what they sold how to fix it and have a good solution and a reason why they do things.
Whether or not they are too expensive is up to an individual purchaser but bashing a company like Clayton is ill form, they do alot for the offroad community, build nice products, and support what they sell, which I think says a lot compared to most of the other suspension manufacturers.