The necks are quite different. The Luke has the V neck, and the JP6 has the flatter neck. The string spacing at the nut is a bit wider on the JP6.
The pickups are different. The Luke has the Active EMG's which give a smoother more compressed sound while the JP6 has the passive Dimarzio's that are a bit louder.
The body shapes are of course different.
The JP6 has a floating recessed trem that is like a Floyd without the locking nut. The Luke has a vintage trem.
In all, the Luke allows you to go from metal to country/blues. The JP6 is more metal/hard rock, but the middle position gives some quack.
Depends who the trade is with. Personally I regret the day I got shut of my Loaded Luke, but needs must at the time. If you can, do a temporary trade for a week with the option to swap back.