The Value Over Time chart in the Portfolio Analysis window calculates a personal return instead of an investment return—so it cares about the relative value of the portfolio on each day.
The two charts are similar in that when Portfolios are charted in the charting facility, the chart assumes immediate dividend re-investment. This is also true in the Return values displayed in the Portfolio Analysis facility. However, the difference between the two charts is due to the fact the Portfolio Reporting chart in the Portfolio Analysis facility actually uses a more complicated performance formula which more accurately reports return.
For example, let’s say you have a portfolio with just one stock in it. Say (by some enviable precognition) you managed to own 100 shares of the stock on its up days, but only owned 1 share of the stock on its down days. The Chart in the main app would show you as 100% into this stock on every day, and so it would show your return equal to the return of the stock. However, the Portfolio Analysis chart is able to account for the varying quantities, and would be able to more accurately display your return for the period. So, in this example, the Value Over Time chart in the Portfolio Analytics facility would look much stronger than the main Chart.