Eventually every one is going to lag the index. The question is how much.
No ETF will perfectly replicate the index (especially not the physically-replicating).
I happen to have previously posted about this is as well, taking and compiling actual price/NAV and distribution numbers.
Result: roughly 1% over a period of 6 years. Not a figure I’m going to lose sleep about.
Both follow different indices, but that shouldn’t make much of a difference either.