The dictionaries list provocative in both cases... I'm wondering if there's any difference.
Провокационный is an older borrowing from the Latin through German, while
провокативный is borrowed from English is way new - it started to be used at the end of XXth century.
провокативный is gaining some popularity (I guess because it's just shorter) it's nowhere near as widely used as
As far as I know, they are completely interchangeable though.
I hardly ever heard the word "провокативный", and it is not listed in most dictionaries, while "провокационный" is a common word. To translate "provocative" you can use "провокационный" only when it refers to something that leads to conflict, fight or polemic. For other meanings word "вызывающий" fits better.
Провокационный is usually about something (supposedly) done intentionally in order to get an expected reaction.
Провокативный can be either about something potentially provocative (able to cause some undesired reaction, not necessarily intended), or (by extension of the term used in psychology*) about someone who tends to behave in a provocative way.