Over the time period where VIOV/SLYV/IJS have been tracking the same index, SLYV has been the best performer, at least when using the following site:
https://www.etfreplay.com/charts.aspxBe careful: SLYV changed index in December 2010, so for my comparison I picked the period 3rd Jan '11 until 19th Feb '19 to be safe:
Total returns are:
SLYV: 140.1 %
IJS: 139.1 %
VIOV: 138.9%
If I shorten the period to 3rd Jan '15 until 19th Feb '19, I get 43.4/42.9/43.0 %. That's a lot closer together, but SLYV again leads the pack.
If I choose either the last year, or the last 2 years, they're indistinguishable (either 6.3 or 6.4%, or 16.0 or 16.1%). That suggests they're now similarly good in terms of performance, but given the smaller gains the differences will relatively be smaller and less distinguishable. Given that SLYV does have lower expenses, I'd probably still favour it (assuming free trades - but it's free at Schwab at least).