Title Insurance Policy rates are the largest fee at closing. This fee is fixed by the state and is a percentage of the purchase price. The fees that are variable are ESCRO fees, doc preparation fees, affidavit fees, etc.
https://www.tdi.texas.gov/title/titlerates2013.html
If you are paying cash then there is no Lendor title policy, survey, appraisal, or home inspection, required. That is where the Lion's share of the savings are found when buying with cash.
IMO
Which title company you use for your cash purchase won't make much difference in cost unless they are quoting you ESCRO, and document preparation fees that are way out of line with the industry normal. You can always call around and check to keep them honest.
That being said, Title Insurance and ESCRO is a very competitive commodity type service industry. At the end of the day you will pay nearly the same price no matter where you go, but quality of service can be appallingly different. So, you should choose a Title company with a competent attorney and a hard working agent that will work for you, and run around and meet people and get things signed if necessary to close on your deadline not theirs.