Hi Sarah.

I wrote a bit about how to pick an index fund in my article here, and why fees aren’t everything: https://pearler.com/learn/read/investment-fees

The long run performance is going to be basically the same given the near identical nature of the indexes they are tracking. So I think other factors are also important, such as the index managers ability to track the index as closely as possible etc.

I personally wouldn’t be switching unless you can point out to an alternative being substantially better. I’m not sure what growth figures you’re looking at by the way – returns for both have been roughly 11-12% per annum for 1, 3, and 5 yrs on each of their websites.