I think sneaking is better tactically speaking. Especially if you operate in pairs. One pair defending, the others sneaking.
If you "slug it" up the middle, you generally are shooting down reds only to have them spawn back in the best place for them to defend their flag. If you do make it to the red base/flag, odds are you will have taken a hit or two along the way so you're somewhat compromised anyway. Once you grab the flag you have to disentangle yourself from the swarm of defenders. If you're lucky, teammates will help fight them back and let you escape. Lots of brute force fighting here.
If you sneak, you arrive at the enemy base with few (or no) defenders and a fresh plane. Use team chat to tell your team to keep the Reds busy (not shoot them down) until you've gotten away from the red base. Once you're out of site of the red base, the only thing you need to worry about are the Reds at mid field or near your base. As long as you and the other blues can out shoot them (sending them to spawn far from the fight) you're free and clear to bring the flag home.
It's no sure bet but it makes sense to me.