The Sabre might be the most widespread ASF of them all and is a fine interceptor, it's just not as tough as the Centurion is.
For a militia in the LC, I'd pick the Centurion - it's in production at Lockheed for a long time, so they've got parts - but the Sabre is a defensible choice even there. Anywhere else other than maybe the Suns (who might have stockpiles they can get at), I'd look at the Sabre first for the parts supply. A bird you can't fly is one that's useless for defense or training purposes.
I personally think the Sabre slightly edges the Centurion in the looks department but that's purely aesthetics. If you're able to entertain the thoughts of Lostech upgrades with XLFEs, there's a couple of impressive Royal Sabres out there, while the Centurion's upgrades are far more limited.