Heh. Why bother with the speed of your juice maker?
The only thing matter in regards of nutrients in a glass of juice are the vitamins and fibres.

In general, plant enzymes doesnt really offer much benefit unless you manage to make iv solutions out of them. Enzymes are usually too big to be absorbed by intestine, assuming they manage to survives our own digestives enzymes and acid.

Vitamins will always be viable as long as there arent significant heat (think cooking temp). No self respecting juicer/blender/food processor would heat up the stuff theyre processing. If it does, you might want to consider changing your gadget as it could be faulty.

Fibres stay as fibrous as long as it arent being minced till too fine. Stop filtering your juice and youll get all the fibres you need from your fruit.

Things you should really be considering is convenience and reliability.