My experience here in 2013 (well, based on a bunch of 2012 redemptions for 2012 and 2013 travel). All of this is of course anecdotal since each of us just books a few awards a year and all programs have their strengths and weaknesses.
- Seems like AA has tightened up in the past year overall. United right now feels much looser overall. I've made 3 different international award bookings for UA seats - 2 using UA miles and 1 using US miles - within 2 weeks of departure. My guess is that UA would show better results on your search simply because they'll display all of their flights plus US flights online. Yeah, you'll probably need to go to Newark. Do you want the award seat or not?
- The 330 day advice is probably still worthwhile if you're trying to snag a max-peak season trip or a highly in-demand premium cabin. But it's completely not necessary on a mundane domestic U.S. flight. In fact, you may want to wait and price that NYC-Florida itin: it might be better to just buy it and save the miles.
- To go further, sometimes the *best* time to book award seats is within a few days of departure. Doesn't really help you for a trip you want to book a year in advance, but this is where holding a high enough elite status to minimize or eliminate award booking fees can be very helpful. Book a tolerable itin as soon as you find it: they keep looking for the "perfect" itin all the way up till the time of the trip.
- Long-range, I'll probably continue to participate in UA as my primary U.S. airline on which to accrue miles. Biggest total network, one-way awards allowed, more options going both east and west (for me). AA would be my 2nd choice. I'm kind of assuming that US and AA will merge into the AA brand and alliance. DL would be my last choice; the R/T requirement is unnecessarily suffocating and simply makes it too hard to find a whole award at one time.