Compared to a single bloomer mophead?

Bloom and leaf sizes can sometimes vary. Like when a recently planted shrub is compared to an older one. New bloomage -with small or recently purchased hydrangeas- can look small-er but that changes as it gets older.

One of the largest mophead blooms is produced by Avantgarde

There are four different hydrangeas in the Endless Summer series and they are all quite distinct. Of those 4, The Original (what most folks refer to as Endless Summer) has the largest flowerhead and is comparable in size to many other - but not all - mopheaded macs. At least it is in my climate :-)

But luis makes a good point - relative size of both the flowers and leaves will depend on siting and growing conditions and the age of the plant and length of establishment in the garden. For example, my Enziandom (Gentian Dome) is known for having extremely large and deeply blue mophead flowerheads but it is only in its second season in my garden and the flowerheads are only about half the size expected for a fully mature plant.