"It is your choice."
Translation:Είναι η επιλογή σου.
απόφαση is 'decision'. επιλογή is 'choice'
I'm not sure if you mean the En meanings or the El meanings. In En, at least, they're synonyms, but I think:
Decision implies a judgement and/or a selection from a narrower range of outcomes. It's a more 'serious' word. So, you'd make a decision over whether to buy life insurance, or whether to find someone guilty in a trial, or whether to move to another city or not. Decision also in many cases implies that it's something you have to do; there's no getting out of it and you have to decide one way or the other.
Choice is a bit less loaded, less serious, and implies selection from a greater range of possibilities. You choose which brand of detergent to buy, or what to eat for breakfast, or what to wear in the morning. You can actually use 'decide' for most cases like this, but you generally wouldn't 'choose' to find someone guilty in a trial. 'Choice' also usually implies a lack of coercion; you can choose something freely, or you can even choose not to choose!
Hope that helps a little.