Front is good. Back increases shoulder separation injury chances and doesn't add anything, so why do it? I actually do so-called push presses for maximum mass (ala lou ferrigno, pearl, etc old school), meaning you do military presses to the front but standing. Because you can push with your legs, you can usually move much more weight strictly and can also force out 2 extra reps cheating with a leg drive at the end of the set. This represents an extra little oomph for shoulders over time. The drawback is that push presses are compounds like squats, deads and bench, so this can really increase your cortisol and lead to overtraining quickly. Strict seated presses involve the whole system much less. Other than that caveat, I love push presses. I alternate those with seated front presses 8 weeks each, and even small 2 week stints of behind neck presses (usually machine) for variety.