Super Simplified Solo 401k ???

[Dan Rudolph]

I established a solo-401k in 2015 and have been a very satisfied client of mysolo401k.com.  I recently recommended this strategy to a friend of mine and he came back with what he says is a free option at TD Ameritrade.  According to him, TDA provides all the paperwork and acts as custodian of the plan.  Obviously this is attached to a brokerage account at TDA.  All for free.

My question for the community:  What are the pros/cons of this type of free plan versus the type of plan that I am using.

Thanks for your help.