I believe that is a personal preference for most. There are good and not as good points to both options.
First ask yourself, 'Do you like to garden, mow, weed, fertilize, seed, etc." If not, you may want to settle for a smaller plot of land or go with the home across from the park.
The question about the park is, "Are there specific hours it is open to the public, will there be kids hanging out after hours, will it attract trouble, do you mind having a lot of strangers hanging out across the street from your house, will you use the park yourself."
If the answer to the majority of those questions is no, again you may want to go with a smaller plot of land or buy the home with the large yard. It comes down to which you enjoy more, yardwork, or people?