There is an engaging lack of subtlety to the Magnolia Collection when the flowers open. Line, form and structure become subjugated to a sensory overload of perfume and color. Passing between trees laden with thousands and thousands of lush flowers, one heady perfume gives way to another, you cover ground strewn with pink, white, yellow petals. Actually what seem to be petals are "tepals", a fusion of petals and sepals. They clearly have substance; thick, rich and textural, the fragrance seems only a natural complement. All this opulence sits at clear counterpoint to the evanescent delicacy of the Flowering cherries, definitely more New Orleans than Japan.
I wouln't want to have to choose, although I suspect that at base I am a magnolia man. I have never been accused of subtle delicacy. The magnolias always begin flowering before the cherries, but there is overlap; this year they are approaching simultaneity. The coming weekend (April 5-6) will be great. If you can possibly visit the Arboretum for even an hour or two, you owe it to yourself to do it.
Magnolias are good garden plants for this area. They don't mind our summers, they are okay with clay soils, they grow as quickly as any other group of woody plants, they have great looking large, furry winter buds, and they look good with their leaves off. Their one drawback as landscape plants is rapidly disappearing as global warming keeps spring temperatures high. It used to be that the early flowering cultivars, if hit by a late frost, would blacken and rot. This doesn't happen so much anymore. Cultivars, eg. 'Galaxy' (a USNA release) have been introduced that start flowering later and late severe late frosts are becoming less and less common occurrences.