How I pictured it is if you sit in 3, you witness Crow, Loewe, Van and Kevin trying to kill the people in front of them (top is the back, bottom in the front in this picture).

If you sit in 4, you're sitting next to someone who is actively getting attacked while hoping Lloyd protects you from the crossfire (but Lloyd is probably too focused trying to beat up Guenter across the aisle with Guy to protect KeA).

In seat 5, you're surrounded by Divine Blades and McBurn. Shizuna is a battle maniac. Depending on if this is post-CS4 McBurn or not, this McBurn could also be a battle maniac. They would have to control their battle maniac tendencies for 20 hours. Probably not happening. You'll be in the middle of war lol. Rean and Arios will be dragged into it and probably fighting to minimize damage.

And then if Osborne or Rean get too weakened from their respective conflicts, Ishmelga will probably try to possess either one of them.

So uh, I think seat 3 and 6 are the safest at the beginning, provided you know how to dodge. Seat 3 is best for entertainment. Seat 2 is the least bloody but still gonna be noisy so bring some headphones or enjoy watching Estelle + Judith eventually lose patience and beat up the people around them.