the convex mirror is the small one, nobody is suggesting otherwise. what is obvious and illustrated by your photo, which does not show a drivers eye position, is the larger (flat) one has the best chance of giving you a view of what is next to you (blind spot) and the smaller gives you a wider view of the vehicles in the distance (if it was correctly set, which it isn't). It probably doesn't make much difference in a small transit like the one you appear to be driving and of course its the nearside mirror that is relevant to the below: