Cherries are a week to 10 days IME, redbuds only a bit longer, and dogwoods the longest. Kousa dogwoods in my yard bloom densely for a month to 5 weeks if you include the early small chartreuse bracts that are there before they become white and fully formed. Cherries, redbuds, and Cornus florida bloom on bare branches while Cornus kousa start blooming as the leaves are finishing emerging and continue with fully formed leaves. It's been so long since I had a Cornus florida that I don't remember bloom length, but because the ornamental part of the flower is actually bracts on these two dogwoods, the "petals" last longer. Cornus alternifolia, the local native dogwood, doesn't have the bracts and the blooms are more in line timewise with the cherry and redbuds. Look also at frost resistance and timing of blooms since your near-ocean location can make for cold late in spring, which can make flowers last longer if it stays above freezing or it might kill them with a frost.

Consider also other season appeal. Fall color is clear yellow on redbud, deep red and late on my C. kousa, peach-like on my C. alternifolia with sun, and a somewhat muddy yellow on my cherries, though that varies some on location, species, and individual plant. Look at winter silhouettte (nicer to my eye on weeping cherries and dogwoods) as well as bark (shiny on some cherries). Fruit can attract birds, and depending on the appeal of the fruit, can add color and movement anywhere from August to spring.

Kousa dogwood

June 1, just starting to show chartreuse. Although this is a terrible photo, I really like this phase.

June 12 whiter, less green

June 22 fully white

and I have a photo from the same year on 6/29 still looking like this. By mid-July flowers are gone and fruits are just starting to develop.

When it fruits, they are about the diameter of a quarter or a bit larger, like one of the larger ornamental crabs. We don't have many gray squirrels here, but this one kept me entertained for a couple of hours one March afternoon. I would guess that Kousa fruits aren't favored food, but they are edible, both for the critters and for us.

The winter flower buds make me think of Russian church spires, and the layered effect of branches looks good.

This particular pagoda dogwood doesn't give a good impression of shape since it's multistemmed - was pre-existing when we bought the house. Single stemmed trees look better.

Slightly past prime flowering, first week of June, but gives an impression of how many flowers there are:

Late July as the fruit is changing from red to purple.

Redbud set to pop 5/2 - Mine is Minnesota strain, selected for hardiness. It seems fairly consistent with wild type ones I lived with in southern OH.

In full bloom 5/10 the same year, but I don't have a series taken in one year to see how long the full bloom is.

Here it is in a different year on 5/20, but it most likely started later that year. I have photos of it in full bloom throughout the month of May, depending on the year; it doesn't bloom for 4 weeks. It blooms with Fothergilla and Rhodie Olga Mezitt and color is somewhere in the middle between the two photos.

Water beads up with a silvery look on the leaves, and the foliage looks fresh and clean all summer here. Fall color is a really nice yellow, about the same as ginkgos.

NH Babe presented a great synopsis and photos of the length of bloom and other qualities of flowering trees. And I especially liked the suggestions in her second paragraph.

Yes, the cherry trees in bloom are gorgeous. That alone becomes the reason many people plant them. Because the blooms are short-lived, I think you need to select a tree for others of its appealing aspects ... the Spring/Fall color of leaves and of the bark ... the forms of the bare branches ... the seed heads. Our Cornus kousa 'Wolf Eyes' shows best, I think, not when it's in "flower" but when the red berries form afterwards; it's close to the steps and the fruit can be seen clearly.

NHBabs is right that you should consider the look/shape of a tree in all four seasons. We have a large Betula nigra 'Cully' in our back yard. It's not so striking in the spring or summer, but in winter it's outstanding! Literally. That's when its salmon bark stands out against the grays and browns of the spent gardens and becomes especially striking right now against white snow.

Another thing to factor into your choice . . . I love flowering cherries, but wouldn't ever plant them here because I have wild cherries with black knot disease which would infect the ornamentals. I have at least two types of wild cherries here (old farmland growing up to woodland) and I love them; the spring bloom really stands out in a creamy light green around the time that the birches and red maples are pushing out their pink, orange and chartreuse young leaves and flowers. If you don't have wild cherries this shouldn't be an issue; I know of a perfectly healthy ornamental cherry just a few miles away that gets no attention or care. If you have the space and don't mind a tree that's just a blob most of the year (unless you choose one with ornamental bark), cherries are gorgeous. It just is only a short time of gorgeous, so you'd want to have things nearby that would grab attention at other times of the year.