The keys to easy-to-read and effective bar graphs are axes and data labels
The top graph has data labels, where the bottom graph does not. The inclusion of data labels makes reading the graph much easier, and no estimation is necessary.
Next, the top graph has a y-axis label, where the bottom graph does not. It is impossible to know what the numbers on the y-axis represent without an axis label. It could be 250g, 250mL, et cetera.
Finally, the x-axis labels are formatted differently in the two graphs. The labels should always be below the vertical bars, as seen in the top chart. The x-axis labels in the bottom chart are inside the chart area, and therefore make it look too clustered.