I think the Betterment AA is fine. Wealthfront is just doing AA with more categories; here is the
Wealthfront Investment Methodology White Paper. But, it is just as easy (and cheaper) to do something with great AA on your own. Vanguard has already been mentioned several times; here is what Vanguard recommends and I also mention two "tweaks" you might be interested in.
Using
Vanguard's mutual fund asset allocator and answering questions for your risk level you get this:
60% Vanguard Total Stock Market Index Fund Investor Shares (VTSMX) (use VTSAX if more than $10K for lower ER, or VTI ETF for low ER with < $10K)
40% Vanguard Total International Stock Index Fund Investor Shares (VGTSX) (use VTIAX if more than $10K for lower ER, or VXUS ETF for low ER with < $10K)
Vanguard just recently changed from 70/30 to 60/40. You can read about it in Bogleheads. 50/50 is recommended by some also, just like forummm did.
Now, a couple of "tweaks" you might consider. Some people may like them, some people may think they are too much work. You only need to rebalance occasionally . . . .
If you look up VTIAX on Morningstar you will see an 86.46% developed, 13.54% emerging market ratio.
Right now, emerging markets make up approximately 25% of the non-U.S. global market capitalization. So, if you want to match the global emerging market cap weighting you can also buy VEMAX or VWO to increase it from 13.54% to 25%. For VEMAX/VWO there is a 17.12% developed, 82.88% emerging market ratio.
So, to solve for right mix you have two equations, two unknowns. 0.1354x + 0.8288y = 0.25 (or whatever % you want) and x + y = 0.4 (40% of portfolio). So, for this scenario you buy 60% VTSAX, 28.2% VTIAX, and 11.8% VEMAX. It's simple math, you can use minverse and mmult functions in a Google sheet to solve simultaneous equations.
Similarly, VTSAX holds 3.79% real estate stocks. If you want more real estate exposure you can also buy VGSLX or VNQ to increase the % to what you want.