Lot's of arguments, but most of them are more of the same.
One argument that I missed was: Apple doesn't publish the RAM, it just tells how great it is. (And let you decide if you want to spend your money on it). Apple don't pretend your iPad will last decades. Heck, AFAIK the average life expectancy of an iPad is 3-5 years.
Just for the sake of argument: give the iPad Pro 8Gb RAM, then it would last what, 5-8 years?! But the battery has a life expectancy of 5 years max, so that is a problem, but say you solve it by using a bigger battery. The LED's in the display will dim to 80% in about 4 years, industry standard is that beyond 80% is not acceptable. So you'll take bigger/more LED's and drive them a bit less hard, now they last longer. But bigger/more LED's need more power, so the battery gets even bigger. More sq-mm chip from upgrading the 2Gb RAM to 8Gb will also use more power, so hey-ho, make the battery again a little bit bigger.
I think a lot of people don't understand/appreciate how complex and how much compromises are made in designing the complex devices that tablets are these days.
It's very easy to comment on design decisions and say: "they cheated out, just want to make more money". And I'm sure they want to make profit (hell, they do succeed pretty well at that).
But you could give them a bit more credit then that, they have made lot's of products that lasted for years and they might have the prognosis that 2Gb of memory is all they need for the next 5 years.
One other thing I often wonder about too: if you buy an android device, you're lucky if you get an update within 6 months from your device-maker after Google released it. If you get it all.
One more thing: can the Samsung Galaxy S3 run Android 6 marshmallow? IIRC it stopped after 4.2 jelly bean.
The iPhone 4s can run iOS 9... Might not be a speed demon, but you do have the choice of upgrading.