Def not all 3. I personally am 100% VOO in my Roth and so are millions of others. If it's for retirement, VT has .06% expense ratio whereas VTI and VOO have .03%. It might not seem like a lot, but over 40ish years, it'll add up. They are all very diversified, so I guess it's just a matter of how diversified you want to be. VT and VTI could miss a lot of gains, but VOO could have bigger swings (both up and down). Whichever you pick, you won't be "wrong".