Like the others, I agree that a middle of the road is a good path to follw, since all information on daylilies has its points and limitations. That said, and based on your climate zone (moderately warm) I'm assuming that rust and seasonal performance (Ev, Dor, Se) are important to you, since you've asked. They are important to me too, especially since we newer peeps are buying without the benefit of really knowing how daylilies will do in our gardens until likely many months (years?!) down the line. I don't want to spend a lot of money on fans that will not make it, perform at a minimum level, or that will die from other causes before I even get to see their blooms...
So, for my first year, and since no one can make a sure prediction, I only purchased the lower-priced ($5) "older" daylilies to start. There are a couple hundred of them (of all types and forms and colors, etc) that were tested back in the early 1990s as being resistant to rust, at least to the only rust strain that was present then, and that is a great place to start. What amazes me about those resistant cultivars is that many of them are very modern looking - you'd be surprised how "new, cutting edge" forms of 2010-2013 often look very, very similar to many from the 1990s, almost as though their look had been forgotten during the turmoil of rust arriving around 1991, and are being brought back now with just some updating.
That said, I dont' pass up a low-cost and good "old rusty" that I'd like, either. The fungus may spread to other daylilies in the garden if it appears, but mainstream science says the daylily's level of resistance is encoded in the genetics of each plant, so one rusty cultivar should not make others weaker. (If you did ever find that to be the case, it would be an important 'breakthrough' that should be formally documented and reported - it would turn the research science in a direction it has never documented evidence for before!). And, even rusty daylilies have an important role to play, especially if you think you might enjoy dabbling some pollen for fun. Some crosses with rusties will improve the offspring, and some will produce a range, but even those that perform less well have resiliance genes for other aspects of disease that, given the possibility of future new-strains of rust, might perform better than those that are doing well now. Sort of like evergreen daylilies in the north... some may not do well in the north right now, but if climate change keeps heating us up more and more, soon those same evergreens might outperform some dormants in warmer northern areas. If we'd tossed or left behind all the evergreens, then, we'd be at a loss in the future when we might need them for warmer country-wide climate.
On the other hand, I'd avoid expensive daylilies that do not do well with rust. Its a big, risky chance to take unless you are sure that you will be okay if they have problems or die with the rust. I like to think that by starting with older, better known, and cheaper varieties first, I'm getting a great chance to learn about daylily history with the least amount of risk. As I understand more about what works for me over the next year or two, I'll be able to confidently explore more expensive, "newer," and more "unknown" performance with a lot less regret. There is a saying in the world of breeding "build your house first and then paint it". I am building a foundation of strong-performance in the plant itself, and then can enjoy more leeway with choosing flowers over foliage.
Sounds like that may be an approach you are taking too, by asking questions and pondering all the variables. Awesome!
Oh, and here's a dumber-than-your question, too!!
FFO ... okay it means "first flower open"... I assume that means the first bud to flower for one single scape on one fan of one variety (and not the FFO of all the garden, as in "extra early fan"). But, since many cultivars re-bloom ... and in my limited experience the "FFO" on the first-bloom and on the re-bloom both are a little "off" (which seems to be why people use FFO; to excuse the look of that first-bloomer)... is FFO only reserved to excuse the first-bloom's flower, or can it also be used to describe a re-bloom scape's first bloom?
Three acorns to anyone who figures out what I just asked.