Can you tell at a glance which asset had a better return since the start date until March of 2009? A plot of total ROI (with all assets starting at y = 0) would make that obvious (for any given end date).
As far as I can tell, the different intercepts just add noise (price of a single stock) that is not helpful to visualize what the plot is supposed to be showing (total returns).
To within a fraction of a percent? Probably not, but to within a reasonable fraction of total performance over 13 years... yes. Look at the initial separation and the final separation and see if the are larger or smaller or look the same. If you can't see it, use a larger monitor. I'd see the point of scaling them when looking at VFISX vs GOOG since there would be a huge range on the scale, but even there you can see the current draw downs are very similar (38% vs 28%). So you can see a 10% (<1% per year) difference in performance between things with a 250x range.
Look at the link for VFISX,VFITX,VUSTX where they start with a ~100% separation (4,5.5,8) and end with very low separation (<+/-3%). In June of 2020 there's a blip where VUSTX goes up 20-25% over VFISX (about a quarter of the original separation) and VFITX is about a third of that or 7-8% over VFISX. So you can see ~3% difference in performance over 12 years or (0.25% annualized).
> To within a fraction of a percent? Probably not, but to within a reasonable fraction of total performance over 13 years... yes.
You didn't answer my question. Could you tell which one had larger returns from the beginning of the period until March of 2009? I couldn't easily tell, and yet VMBFX has a total return of 127% and VFINX 89%
As far as I can tell, the different intercepts just add noise (price of a single stock) that is not helpful to visualize what the plot is supposed to be showing (total returns).