The difference being that Hibiscus syriacus is a deciduous shrub so it can live through the winter as a dormant plant rather than suffering through winter with an abundance of tender leaves.
There are some beautiful hybrids of this plant with varied sized flowers and colors. It is also fairly low water once it is established. Rose of Sharon is a large plant usually 6-8' tall and can be purchased as a single trunked small tree or as a multi trunked large shrub.
They have a bit of yellow fall color and lovely small leaves.
Plant in full sun and in a spot with good air circulation. Water well at first to avoid wilting then taper off water to once or twice a week. Trim only for shape and do not shear, instead selectively prune away foliage that is diseased, dead or in need of clipping.
Pictured below ar Hibiscus syriacus 'Minerva', 'Diana', and 'Red Heart' (in order shown)