VXUS and VFWAX (or the ETF version VEU to compare apples to apples) track very similar but different indices. VXUS tracks the FTSE Global All Cap ex US Index, while VFWAX tracks the FTSE All-World ex US Index. The most notable difference is that VXUS includes over 6000 stocks, while VFWAX includes about 2500. VXUS is also the larger fund. Both are just fine, and the results are extremely similar. The larger issue is your focus on ROI for a single index fund rather than your overall investments.
The thing about individual fund charts is that you can't just look at them in isolation. You have to consider the big picture of how each fund fits into your larger portfolio over time. Pretty much every stock fund tanked in 2008 and would look bad on that chart, but that doesn't make them a poor long-term investment in a well-diversified portfolio.
It's sorta like baking a cake. If you only add individual ingredients that taste good on their own, you'd leave out the flour, eggs, and baking powder and would only add butter, sugar, and chocolate. That may sound good theoretically, but it would make a pretty crappy cake.
Just like baking a cake, you first need to learn how individual assets work and how they contribute to the overall recipe before you can prepare a good portfolio. Here's some
more info, if you're interested.