SD IRA v 401k

[Jason Smith]

I have been trying to determine the best route for me, but I am finding too much contradictory information.  

I am transferring my old 401k from a previous job I to a real estate investing portfolio. Whether it is SD IRA or 401k I can't decide. I have a decent amount of money in the account and plan to buy and hold with this money.

My question, over the long haul what is the best option?  Can I even start the 401k if the funds were in a previous 401k, are the fees for SDIRA so high as to be cost prohibitive?  

Sorry if this has been discussed so many times, it's just hard to take 20 different threads asking basically the same thing and getting 20 different responses for each individual.