I like the option of 1 or 0 as in OxygenBasic, only because as many stated lots of other languages use 0.
It is nice to have the flexibility.
If the earlier programming languages were from a perfect world, I think using 1 would have been better as Eros chose
in thinBasic.
But for the size, I think saying array[10] would be 10 elements total and not 11.
indexbase 0 that would be 0-9
indexbase 1 that would be 1-10