Need help in deciding FS1 or FS2 for my son

My son is 3.5, will turn 4 in September. We are moving to Dubai in July. He will be enrolling in Sep session. He is going to Pre Nursery in India however we have relocated 3 cities in the past 8 months so this is a transition phase which i want to manage very carefully. I want a smooth transition and not stressing. He is just getting adapted to speaking english, he understands more or less.

Which grade would be better for him FS1 or FS2?

I am solely considering his emotional quotient right now and don't want to pressure him into competition or anything.