It's really up to you.
We routinely plan at least 2 trips a year to Disney, so - for us - annual passes make good sense, financially-speaking. They include park hopping, and I find I really appreciate having that flexibility on a long trip.
However, if you're planning to stick to one park per day, and you'll only be making one visit in the year, then single-park tickets can be a good deal. You can leave and re-enter the park on the same ticket, so you can enjoy both the morning and the evening events, while still taking a mid-day break. And if you decide you're done with the park for the day, you can always head over to Disney Springs for shopping and dining, or take in some of the activities at your resort (like the pool, or an evening movie).
There's no wrong choice here.
(Edited to add: I'm sure you already know this, but you can't use a one-day ticket to enter one park, and then try to use a different one-day ticket to enter another on the same day. Once they have you in their system, you're locked into that park. If you try to enter another park, even if you have more one-day tickets in your account, they'll direct you to the ticket kiosk and tell you to upgrade.)