I vote for Target Retirement 2060.
If you already have done a little studying on investments and you are sure, for your personal investing reasons, that you
a) Want to be 100% in stocks, nothing but stocks, nothing else, and
b) Want your stocks to be 100% U.S. stocks, nothing but U.S. stocks, no international at all, then,
of the four you listed,
Total Stock Market Index admiral VTSAX, because it is the most normal, neutral, plain vanilla of the four. It is a "core fund." The Index 500 is basically an outmoded total stock market fund, while the others are sauces, seasonings, to be mixed in or not depending on your investing strategy, but not to be used as entire holdings in themselves.
If you want to be 100% in stocks, nothing but stocks, but you don't want it to be 100% U.S. then you might want to consider the Vanguard Total World Stock Market Index Fund, VTWSX.
500 Index is the S&P 500. It is, basically, an old index and old fund that were normally purchased because people wanted "the whole stock market," and for a long time the S&P 500 was considered a good proxy for the whole stock market. Actually, it still is, but the newer total stock market indexes are closer and more accurate. So, for most people, given a free choice, the reason for wanting the 500 Index says they should have a slightly preference for Total Stock Market.
VGSLX is, in my opinion a "specialty." It is supposed to fluctuate somewhat differently from the stock market as a whole, though it hasn't been doing that lately, and therefore, according to one theory, adding a controlled amount of VGSLX to the total market should improve the overall portfolio. But you don't invest JUST in VGSLX.
Exactly the same thing is true of VSMAX. If you use it, you mix it in, you use it as flavoring or seasoning, you make it your whole portfolio, use it as a "tilt." There is the additional wrinkle: the people who advocate a "tilt" to small-company stocks tend to think that "small value" is better. That would mean using Vanguard Small-Cap Value Index Fund (VSIAX).
Annual income twenty pounds, annual expenditure nineteen nineteen and six, result happiness; Annual income twenty pounds, annual expenditure twenty pounds ought and six, result misery.