PeterH:
cjdelphi:
with each iteration of the loop does a local variable get created (c/n) and recreated over and over again?Yes. Automatic local variables are allocated on the stack and thrown away when the stack is unwound at the end of the call. In general, the more tightly you restrict the scope of the data the less chance there is for dependencies and unintended interactions between different parts of your code. This is why use of global data is best avoided where possible, and use of local data and arguments is generally preferred.
With 2k RAM I prefer globals and keeping control of my code. A few locals don't hurt but whole buffers in short often-called functions, it's good to be aware of because some day you might be writing code that needs to be fast rather than 'do it this way every time'.
awareness != mandatory practice
I've likened using C++ Strings on Arduino because C++ Strings are okay on a PC to putting a bathtub on a bicycle just because your house has one. I still feel the same. There's a lot of coding practices I've happily done on PC's that I wouldn't think of doing on Arduino.