You are fortunate to have all these choices; in most school districts the decision is made for you and the schedule set for you - no choice between half- or full.
You know your own child best. She will be older than most K students and that could work for or against her: If she is in K full day she may find that more stimulating and be ready for it. But she could have the opposite reaction --she may find it boring and stifling if she already knows things they are doing in K and has to sit through full days of letters and numbers and other things she can already do.
So ask yourself: Where is she on her learning? Would she get a lot out of being there full day --both socially and academically -- or would she be spending time doing things she may already know and thus would be bored?
Investigate now, not next fall; find out what they cover in the curriculum of full day versus half day. Sometimes full day is really just a half-day worth of actual curriculum learning with more play, a nap time and snack tacked on, frankly; in other cases it's much more learning going on. But I suspect that if your district offers both options, it's the former situation, and that would make me question whether she will really get more learning time in a full day or just more socialization time. Nothing wrong with socialization and play -- just investigate and think about what would work best for her.
My child was in the last year of half-day K at her school; virtually the entire school district went to (mandatory) full-day after that. I was glad she was in half-day because it gave us lots of time together and she wasn't napping at that point but did need her "down time." She was five and then turned six in her K year. But if you have other kids to juggle and a job, you may find that full day does work best. If you choose half-day you may want to do more activities with her on those days she's at home -- kids' science experiments, reading at the library, kids' book clubs (many libraries have them now), math at the grocery store as she helps you total stuff -- things like that.