Dwarfs are shorter so easier to pick since a ladder is not needed, they fruit faster, sometimes in 1/3 the time. They have a shorter life span, may need to be staked, and require more trees to be planted in a given area since they are smaller. All fruit trees are grafted if you are talking apple peach pear etc.

Scott

I'm not sure about the shorter lifespan claims.
My dwarfs are around 20 years old. Nearly the same for my semi-dwarf. If I see any death starting it's on the semi-dwarf.
It sounds like the dwarf Upick I went to was started in the 70s.
It's hard to guess if they're standard or semi-dwarf but we figure my niece's trees are 30 years old and they're on their last legs.
It's also hard to judge because my 20 year old Stark trees are not on the same roots as my 1 year old Stark trees.

Dwarf should bear faster.

Semi-dwarfs are much easier to cover with bird netting, especially if pruned low. As mentioned above, also easier to pick and faster to bear. Since they're all around smaller, you can plant many more in a given area and try out more varieties- diversification reduces risk. Smaller trees have shallower root systems, more dependent on regular watering, but less need for deep soil preparation. Also much easier to spray with a small sprayer should the need arise. Almost every tree I have is semi-dwarf.

How cold hardy are dwarf apple trees? The only ones I've seen in our area are multiple grafts, but I would prefer a gala. I'll keep looking, but I may have to order from a nursery. Any recommendations?

Lavender:

Call one of the nurseries in your area with that question. Van Well Nursery and Columbia Basin are happy to work with homeowners on small orders. Their trees are good and prices reasonable.