As long as expense ratios are comparable, there is so little difference between the two that is worth mentioning. They are almost universally cap-weighted funds, so they're dominated by the same large companies.
All else being equal, I'd choose TSM just because it is slightly less dominated by a few larger companies.
In my taxable account, I split my US equities evenly between a TSM and small cap fund (SCHB and SCHA).