Which 1?

[Thracian Princess]

well, the debate between pro 0 turn and pro 1 turn is ultimately endless

Meh, I say screw debating. Just play whatever one you want and be happy with that. But that's just me

[naq]

you must mean under-populated

No. Over-populated comparing to AI.

Well, for me, 0-turn has some advantages: First, I only have to make one most developed city as the recruitment center for each front (others can be developed in culture or economy instead). Second, I can train an army whenever I want. Third, I don't have to keep track of the recruitment each turn.
For the spamming problem, too bad the only solution is taking the enemy's cities as fast as possible.