I think most here know the 'Total Market', because it's market cap-weighted, is almost identical to the '500 Index'. Over the past couple decades, the concentration of even more of the money into even fewer companies at the very top has made that even more true that it already was. And even more worrisome to me.
Long term, you ought to do a TINY bit better in the Total Market than the 500 -which is 100% because you have a TINY bit of Mids and Small Caps. So what if you had a much more meaningful chunk?
I've actually preferred the Mid Cap (blend) over the Total/500 as my primary fund, and have done much better because of it. It didn't get killed in the dot com bust (no 'Lost Decade' despite being 100% stocks), and while it crashed ~5% harder in the 2008-9 crash, it recovered completely just as quickly as the overall market.
In the past decade (~2007-2017) it beat the market by a little, but pretty similar.
I do 60/30 Mid Cap and Total Market (the other ~10% in 3 tech funds). It lets you do some rebalancing within stocks if you want to (I've never bothered).
Mid Caps follows the market ups and downs almost perfectly, but have had better upside highs over the long run, and no meaningfully greater lows. The price is ~.03% higher fund fee and a bit more volatility. Def been worth it to me.
I also prefer Mids to Small Caps (whether growth, value or blend) because the Mid index is actually weighted to lots of multi billion dollar Large Caps of big names we all know. It's pretty much just a block of ~350 companies right below the top 500 (market caps actually overlap even).
That group has more room to grow than the Mega Giants, IMO. The losers get kicked out at the bottom, and kicked up at the top.
The Small Cap has to keep the lagging losers, and the Total/500 has to keep the bloated Mega Giants. I think that's why the article recommends Small Cap VALUE -because if you're risking $ on the smallest companies, it's probably wiser to aim for the ones considered safer 'value' bets.
I also notice a lot of these articles totally ignore that there even is a Mid Cap Index. They act like you're either in Large Caps or Small Caps. I hate that. Mid Caps appear to be the 'Goldilocks' Index to me -or at least they have been for many decades. They might be total shit going forward, but there's zero evidence for that guess, so I can't see any reason to change my position.
Guess this also goes with 'can you beat the market' threads. Yes... 'Overweight the Mids'.