Assault has much more depth to it than just preworkout energy. Jack3d is a good product, but its claim to fame is the amount of energy you get from it. Assault on the other hand has ingredients that are clinically proven to increase performance, recovery, and strength for your workouts. Now don't get me wrong, Assault still gives your plenty of energy but it does not get you overstimulated or off the wall. Finally with Jack3d you are going to mostly likely be taking 2-3 scoops per workout, where with Assault you will not need to take more than 1 scoop per workout.
To recap it really boils down to personal preference and what you are looking to get out of your pre-workout product. Just take a look at the ingredients in both products and you will see that they are very different products despite a couple similarities. Let me know if you need more clarification.
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