I was at a weekend continuing education course and the topic veered toward small cap funds. It was mentioned that the S&P 600 has outperformed the Russell 2000 historically. I've held my small cap allocation in Vanguard Small Cap Value Admiral Index Fund (VSIAX), but the S&P 600 ETF (VIOO) has outperformed it by about 1% a year for the last decade. Should I replace VSIAX with VIOO? Please let me know what you think!
As Indexer has pointed out, one is small-cap value, one is just small-cap. Small Cap Value can underperform for decades at a time, you need to base these decisions on much longer holding periods.
But: you'd still be well served by changing indexes, because VSIAX uses CRSP US Small Cap Value Index, which isn't as strongly exposed to SCV as the S&P 600 Value index is. (Russell 2000 meanwhile suffers from front-running, but note that VSIAX follows the CRSP index not the Russell index.)
You can compare the performance of these indexes by using the following tool, it's easiest to compare VBR (the ETF version of VSIAX) to VIOV (which is Vanguard's S&P 600 Value ETF):
https://www.etfreplay.com/charts.aspxOut of the S&P 600 Value ETF's (I have no idea about funds - but there's no good reason to use funds over ETF's anyway) I prefer SLYV since it performs best (might not work for some people if they have to pay capital gains taxes though), VIOV and IJS are solid backups if you want to avoid capital gains distributions. The performance difference is minimal, SLYV is generally a fraction of a percent ahead over years.