Ram parts, aluminum or heavy duty plastic????

Any experience comparing the aluminum double socket arms to the heavy duty plastic ones?  I'm going to stick with aluminum for the bases, but wonder if the plastic sockets would be lighter, and or hold/clamp as well?
This is for the fish finder only. The rod holder will be whatever it comes as.

RAM-B-201U vs. RAP-B-201U
RAM-B-201U-A vs. RAP-B-201U-A

I have the double socket plastic for my GPS, and it works great.  I've never seen the aluminum models, so no input there.  They're definitely sturdy if that's what you're wondering.

I'm sure there is some weight savings choosing the plastic over the metal, and possible floating parts being plastic?
The cost is lower for the plastic units, as it is probably easier to manufacture.  I just need them to support the weight of my Cuda. 
It would also be desirable for the plastic to fail in a crash, before ripping the mounted base off the kayak.  I don't plan to mount my Cuda in the sail mast hole as I want to keep this option open for future plans.