I've spent a few hours looking into this, and this was the best explanation of the main self-employment retirement accounts I could find.
Solo 401(k) vs SIMPLE IRA vs SEP IRA
http://www.obliviousinvestor.com/sep...-vs-solo-401k/
You can even do a Solo Roth 401(k) which will allow you to have both pre-tax, and post-tax funds, for those of you who aren't sure if you'll be in a higher, or lower tax bracket when you retire. Best of both worlds? Worst of both worlds? I don't know, I haven't researched that position yet.
Anyway, with a possible max annual contribution of $54,000 for a both a Solo 401(k) and a SEP IRA, (but easier to do with Solo 401(k)), those both look way more useful than the standard IRA or Roth IRA with a max annual contribution of $5,500. I think for me, the above two mentioned are the way I'll go.