A.J.
Hi I.,
I would say it depends on your school district and your son and your financial situation.
Are you in a good school district? Many good school districts design their curriculum in a way that begins preparing the children in Kindergarten. Also consider what it would be like for him socially when he is to start 1st grade.
Does your school district offer half day or full day? Do you feel your son will be (there is a lot of growth over the summer) mature enough to handle full day if offered (most 5 year olds are, but their are exceptions)? Does the day care offer a wrap around program if the district has half-day so he can be bused there after school while you are at work?
Public school is paid for through property taxes of homeowners in your district so you will not have any more out of pocket expenses other than taxes. Can you afford another year of tuition?
In my opinion, if your school district is good then sending him to the district kindergarten program will be most beneficial. I am sure your daycare has loving caring wonderful teachers but kindergarten teachers in the public schools have master's degree or are working towards one and do wonders for their students (I am a former Kindergarten teacher).
On the other hand if you decide to send him to the day care's program I am sure he will feel comfortable from the beginning and thrive.
Regardless of your choice, stay involved in his education, keep an open line of communication with his teacher, and he will do very well.