I hate this question. Why are you trying to "build" hours? For a crappy airline career? It'll take you at least 5 years (heavy unit) or 3 years (fighters) MINIUMUM to get the hours for an airline job, assuming you fly your a** off the whole time. The entire time you are "building" hours for something else, you're expected to perform. You'll be expected to be a copilot, a two-ship flight lead, an aircraft commander, a 4-ship flight lead, an IP, an EP, perhaps a weapons officer. If you're entire focus is on "building" hours, then you'll be crappy at all of those. If you're goal is to be a professional pilot and be good at what you do, then pursue whatever avenue gets you there, and focus on what you're doing. If your goal is to "build" hours for some imaginary future job, then leave the military alone and go find a crop duster job.