I was pretty into sea kayaking before getting into sailing. What are your goals besides getting out on the water? That helps to determine which one you will enjoy.
Kayaking gives you a much better ability to explore the coastline at a very close up and personal level. It is a great platform to check out the wildlife from.
Sailing makes it a lot easier to cover long distances in one day. A 30nm day is long on a sea kayak, but it's pretty easy to do 60nm days on a sailboat (coastal cruising, not sailing 24 hours through) and longer if you take full advantage of the tides.
Both offer plenty of chances to learn new skills. Sailing efficiently is one of those things that seems simple but takes a lot of time to master. The same is true of handling a sea kayak in rough and tight technical conditions (like playing in rocky surf).
I found that the navigation and planning skills from kayaking carried right over into sailing. I learned how to read charts, understand back eddies, read the water, and plan a course through kayaking. All of the same stuff matters for sailing.
I would add a plus with a kayak is transport. I have both --- though very different sizes (8 ft Kayak and 15 ft sailboat).
Here is an example --- Last year a couple friends and I wanted to drift/paddle down the Saranac River. (we didn't want to paddle back) So we dropped the kayaks at the starting point and a truck at the end.
1) very few boats and no sailboats could have made it down the river
2) even a row boat would have been more difficult to transport back than three kayaks
3) for the most part each of us had our own water... camera, sunscreen and general needs on each on our own kayak.
If you just want to get out there and go cruise a kayak will get you from anchorage to shore. You'll probably end up wetter, but with less expense. For a longer cruise a dinghy is better because you can transport more stuff, water, fuel, food, friends. On our boat, we have both and plan to use both this weekend. The dinghy is fun for runnign about and the kayak is fun for exploring.