Just Parfum is typically more expensive than Eau de Parfum because it has higher concentration. Some folks feel the concentration will change the character of the smell even though the chemical composition may be identical. Sometimes a perfume house will alter slightly the chemical composition of it for each strength - doesn't happen often, but Guerlain and Chanel both have been known to do this.
When my wife was faced with a similar conundrum, she ended up with the EDP since she fell in love with Jicky with a sample of the EDP.
If you have not sampled both, I'd recommend it and then decide.
If you have sampled the EDP, and are wondering if the Parfum would be "better" - remember you LIKE the EDP, so that should weigh in.