Re: We should use neither
"The clumsy "shield" system is for people that can't solder a stripboard / vero and micro-controller on it. "#
There's nothing clumsy about it - it does its job very well. And soldering stuff tends to be non reversable unless you're exceptionally careful so it wouldn't be a good idea for a prototyping board.
"It's not directly comparable to the Pi, as entry level Arduino can't run Linux, they are a target."
The arduino is a microcontroller system - the OS is your program. The Pi is a small computer which IMO uncomfortably straddles the low end computing and high end controller hardware arenas. Its too low powered for most proper computing tasks and too "fat" for serious controller tasks where you don't usually need or want a full blown OS with all the apps and your program running in Python. You want something lean that does no more than it needs with the program compiled as a binary for speed and efficiency.