Personally, I find the latter easier to read too, as it’s not stretched across the long screen. If the numbers are too small, you can rotate your phone or zoom in.
There is less data in the new graph.
The old graph makes a clear distinction between mature and young cards.
The screen doesn’t need to be rotated for the old graph to be legible.
The new graph doesn’t fully display in landscape mode (see screenshots added in OP).
There a gradiant in the colour in the new graph that corresponds to nothing.
Well you’ve scrolled down in the landscape comparison to look at the text below the graphs, so that’s not entirely fair
The gradient is primarily for aesthetics, but it also conveys how far from today the counts are. The young/mature division was deemed to not be important enough to include on that graph, but it can be seen in the reviews graph if you want to get an idea of the ratio.