My employer lets me to pick VTI as my employer contribution to my 401a. Should I continue to invest in VTI on my own or just let them do it?

They'll contribute more bi-weekly to VTI than I am currently doing on my own. But I can't withdraw it until I'm about 60. Should I sell my position of VTI in my own portfolio and redistribute that money and future contributions to my other stocks? Or continue investing in VTI on my own in addition to my employer?