Fortunately, there is no wrong choice. The Mojo 60 and the Primo 60 are both great 3D planes that are a significant step up from the planes you have been flying.

If you already have a DLE 20, then then the Primo 60 would be the best choice.

But building a Primo 60 won't keep you busy until October. They build pretty quick.

Therefore you should buy and build both a Primo 60 and the Mojo 60. Building those two should keep you busy until about August at the latest, then you have to come up with something else to build to stretch it out to October.