Welcome.

At work we have both single and dual extruder machines. The most helpful feature for dual extrusion, in our opinion, is using dissolvable filament for support. This can be very useful for complex designs, as removing the support material can be both tedious and damaging to your final part.

As I recall, fitting a dual extruder to an Orion is possible. However, it may be difficult. I'd recommend checking the SeemeCNC forum for details. The Printrbot Metal Plus looks like a good machine, and I'm seriously tempted to get the upgrade kit to modernize my home printer.

If your budget will stretch to it, I'd probably go with the Printrbot for simplicity.

Good luck!