I wonder why you want to do self-care? Just curious. If your barn will be full with full-care boarders, then it seems more beneficial for you to do full care. Barns around here are full with a waiting list even if they only offer full care.
As a full care boarder, my perspective of being in a barn with self-care boarders is that I would rather not. What I found was: the barn would smell and/or have flies in the day because the self-care boarders may clean their stalls at night instead of morning. Some owners would have "emergencies" or work late and not clean their stalls for more than a day. Some horses would not get turned out if the owners were responsible for this task.
Some horses would not get fed in a timely manner and would be frantic in their stalls listening to the other horses get fed (someone already suggested not including this in your self care option).
I know there are many responsible owners who take impeccable care of their horses and want to save money by doing self-care. Yet there are many very poor horse owners who do self-care because they don't want to spend money on their horses. At least if an owner is negligent, in full care boarding the horse is cared for.
Another reason is that I'm always at the barn. I sometimes go first thing in the morning before school, 3:00-5:00 after school, and again 9:00-10:00 during the winter. I trust that my hay and grain is of the quality and quantity I want her to have. There have been times the barn owner has forgotten to feed my horse. Thankfully, I noticed and gave her some when I came to the barn. Another reason is that the water is always dumped, scrubbed clean, and refilled straight from the spout. The barn owner fills the buckets with pre-set out buckets of water from a day or two before. The barn is a conjoined arena, so the dust is always being stirred up and getting in the water buckets set out.
Another reason is most full-care barns around here aren't cleaned well. No offense to the owners, but they have fourty-some horses, and the boarders are lucky the stalls get cleaned to a reasonable quality. I don't want my horse getting thrush, thank you very much.
The last reason is... it's cheaper. Full care board around here can go over $550/month. Why should I pay that much if I'm still going to go down and do everything myself anyway?
I prefer to know that my horse is taken care of. I know she also appreciates me coming and seeing her every day for at least a few hours. A horse can't be trained unless you put the time and effort into it. With a rescue or fresh horse, just being around them is training.