Hey,
I have a Walker Bay 10 and a West Marine 13/4' sit on Kayak. I use both.
Dingy Pros:
Can fit 2-3 people and / or lots of gear
Has a floor so everything stays dry
Has a 2.5 hp outboard engine, so it's quick and can cover long distance
Decent rowing performance
Pretty stable
Fairly easy to get from dink to boat and back again
Donghy Cons:
Heavy - well over 150 lbs
When it rains it holds a lot of water which needs to be pumped out / bailed
Kayak Pros:
Pretty light - easy to move around the beach and can haul aboard the boat
Easy to paddle to the boat
Fun at anchorages, beaches
Kayak Cons:
Very limited cargo capacity. I will wear a back pack to take a few items, and maybe can stow one bag
Can get wet
Difficult to get from Kayak to boat and back again
Not very stable
My boat is on a mooring. My dinghy stays on a dock about 1/2 away. It's too far to easily and quickly row so I usually take the dinghy to the boat. My kayak is in a rack on the beach, about 100 yards from my boat. So if it's just me going to the boat I will take the kayak. But then at the end of the day I need to drag the kayak up the beach and put it back in the track, which is a pain, especially if I get back at low tide.
Hope this helps
Barry