What size Burton Apres jacket?
Going by your height and weight i would say you should go for a medium size jacket.
Difference between the Rab Latok jacket and the Rab Latok Alpine jacket?
The Latok Alpine Jacket has a heavier lining inside of it, for extra warmth. However, the price goes up accordingly, so it really depends on what you are planning on doing with the jacket. Good Luck!
What size jacket should I buy?
Invisible, it also depends on what you're likely to wear under the jacket. (I'm assuming this is an outer-wear jacket, not a suit-coat jacket. Hope I'm right.) A 40R will fit properly over a shirt and a thin sweater, but it may be tight over a sweats...