Depends on who you fly and what the trends on their fare schedule fluctuations look like, and also WHEN you fly (seasonally). Watch patterns over time for routes you fly frequently.
We like Southwest, who typically doesn't release fares until 6 months or so out, then I book first day and thereafter watch for re-bookings at cheaper rates (sometimes it gets cheaper, sometimes not). So definitely
DVC first with Southwest.
We also fly Alaska since they're cheap and fly a lot of the direct routes we need (OAK-Maui, etc). Their flights tend to be released far in advance then prices fluctuate, often getting cheapest within about 3 months to 1 month of travel, then spiking at the last minute, but sometimes its cheaper to book 8+ months ahead ... so most of the time I'll book DVC first, but if I see a great fare farther out, I might grab it and if I can't get the exact dates I need then don't mind staying a few nights in a hotel on either side of my DVC stay.
If you're going with the legacy carriers (eg. United, Delta), especially for certain times of year, it can be more cost effective to book 14+ months out. We do this when we fly Delta into Salt Lake City for our annual ski trip for our other timeshare that we can book at 12 months out, because its such a highly sought-after route, waiting to book can be $$, and Delta has the SLC market sewn up.