Vanguard's will have lower expense ratios than the equivalent iShares funds.Each fund will track a pure Treasury benchmark and no longer hold government agency-issued securities. This includes debt issuance from Federal Home Loan Mortgage Corporation and Federal National Mortgage Association, known as Freddie Mac and Fannie Mae, respectively.
The benchmark changes will occur over several days in the fourth quarter of 2017 and aren't expected to affect the funds' expense ratios. And while the fund names will change, their tickers will stay the same.
SHY- 0.15%
Vanguards 1-3 year treasury- 0.07%.
Like they said though, they still have non-Treasuries among their holdings for now.