Before I give my answer, I want to explain my background. I am an educator. I have taught Kindergarten and First Grade. I am also a reading specialist AND I am a mother of three. My children are spaced out ten years. My oldest went to half day kindergarten. He is currently about to enter 5th grade and he is above grade level at a parochial school that has strong academics. My second went to extended day kindergarten at the same school. He is about to enter 2nd grade and he too, is above grade level, perhaps even higher than his brother. I don't think that this has anything to do with the fact he spent two hours more a day in kindergarten. My youngest is 11 months. Ironically, I was just thinking the other day, that I would want her to attend a half day kindergarten.
Of course, this is assuming that she is as bright as her brothers. If she struggles academically, I would want her to have a longer school day. If I see that she is struggling academically, I would hold her back a year and start K when she is six. Her birthday is the end of August.
Schools these days tend to be very academic. A longer Kindergarten day allows for the teacher to expand some subjects, add in art, music, etc, or stuff more into everyday.
Yes, you certainly need to think about your child's developmental levels and what she can take but you also need to examine how well she is doing academically. Does she know her alphabet, not singing or chanting, but out of order, capitals and lowercase? Can she write her name? Can she read some words? How high is she able to count too? Depending on the answer, may help you decide where to send her. If she know the skills I have listing above and can actually do even more, she may just need the half day program or you can check to see if one of the full day programs have time for other subjects like art, P.E. , social studies, etc.... If the full day programs focuses on early reading and math skills, and she is strong academically, she may be challenged to stay engaged. However, if she has not acquired the skills above, the extra time may give her the boost she needs.
Most Kindergarteners and 1st graders are exhausted the first six to eight weeks of school. Each afternoon when I taught first grade, at the beginning of the year, I would have kids that actually fell asleep at their desks.
Kindergarten teachers will accomadate their young students, getting them ready for a more challenging day later in the year. It may be easier to have her in a longer day. You know her day is more streamlined.
Good luck, I am sure that whatever you choose will work out for her. Remember to have a positive attitude with your daughter when discussing school. It will give her the confidence to go foward too.