As I remember it the second one is a hybrid. There are many cultivars of P. japonica. The new P. japonica 'Katsura' combines pink flowers with stunning mahogany(?) red new growth - a novel combination. The new leaves are so strongly colored they look fake.

'Dorothy Wykoff' is a selection of p. japonica. 'Brouwer's Beauty' is p. japonica x p. floribunda. As a practical matter, 'BB' will become larger in time than DW. In my experience, the flowers of DW are larger, more abundant and in longer racemes than BB which displays its flowers in a more upright way - a trait inherited from p. floribunda.

There are many more pieris cultivars to choose from. For 50 weeks or so out of a year there is no bloom, so picking one with interesting leaves - variegated, glossy, etc. - is a worthwhile priority.