A few comments:
First, maizefolk has done a great job of doing the math. I think his analysis does miss one thing, though, and that is the opportunity cost on the tax benefit over those 18 years. In other words, if you take that $232 in tax savings and invest it, the growth on that $232 will offset some of the annual fees and expense ratio costs mentioned over that 18 year period. Depending on what you do with the tax savings, that could matter a lot or not much at all.
Second, as to how much to save, it's highly personal, highly variable, and the amount can change even up through the college years. Personally what I chose to do is look at the College Boards Trends in College Pricing report, figure out what I wanted to contribute, and then use their numbers for both the current cost and the inflation adjustment to generate a targeted future amount. I then calculated what I had already contributed and what it would grow to, and then I just kept shoveling money in until what it would grow to equaled that targeted future amount.
When my kids started into the college years, I gradually switched from College Board numbers to actual numbers based on the tuition bills I was receiving. I've gone from "I don't know if I'm saving too much or not enough" to "Oh my gosh, I've over saved by a lot" to "I don't know if I'm saving enough, but probably not" as my three kids have changed their plans. At this point I have one who is graduating next month, and two who are approximately sophomores. My plan now is to monitor the situation, use their college funds until they're gone, and then figure it out from there if I happen to need more. Fortunately by the time you get to my point in life, if you've planned well and done all of the good financial moves, a year or two of college tuition is probably a somewhat large rounding error in the big scheme of things.
One last comment: I believe some plans restrict the number of rollovers you can do per year or per 12 month rolling period, so if you do decide to do the extra work to have the best of both worlds, be sure to research that as part of your planning.
Congratulations on the daughter!