Let's say we have a Basic program that has two variables, one of them is a string and the other is an array of strings. They both have the same contents. For example,
LET A="TEST" ARRAY B B="T" B="E" B="S" B="T"
Ignoring the fact that making an array takes more code, which one would take up more memory (in RAM) to store? Which one is more "efficient"?
If you're talking about just 1 string, then the variable would be more efficient because you won't have to recall 4 data slots and combine them together. Arrays are only more efficient when you have multiple strings you need to store, like a list of people's name.
I am not an expert on BASIC, but I believe all strings are handled as arrays of characters. Therefore, "TEST" and ["T","E","S","T"] would take the same amount of space. I would go with the option that involves less code, as that increases readability.