I need super basic Help with Hardware choices

Also look at the Mesa 7c80 and 7c81 as the Pi plugs directly in to those.
But the Ethernet options are cheaper if you consider that the 7c81 still needs adapting to wire to the stepper drivers.

Do you currently own a PC that you can experiment with? If you do then that would point towards the ethernet solutions. Though personally I prefer the directness of PCI (If I was building a plasma cutter I would consider that direct connection a bad thing, and definitely go ethernet then, for the isolation)

Aaroncnc wrote:

I feel the spi are is for things that lack the first 2 as they seem to come at a higher price point and more hassle.

Basically, yes.

But functionally they all work very much the same. With the odd exception that I think that the EPP parallel port controlled cards (7i43 for example) actually run at a faster base clock than the others.
However there is no reason to choose one interface over another except for convenience of connecting.