Reply to VCI100SE Upgrade?

So I'm looking at purchasing a VCI100 from DJTT, but I'm wondering if anyone can shine some light on my situation.

I see that for $650 I can get the VCI100 SE w/ a sound card, and for $850 I can get the VCI100 Arcade w/ a sound card.

And now to the questions:
What is the difference between these two controllers is aside from the arcade buttons on the bottom?

And if they are the same, why wouldn't I buy the SE, a VCI-100 Arcade Overlay for $30 and 8 arcade buttons for a whopping total of $16 and build my own Arcade out of an SE?

Thanks for any help you can offer!