We had lived in Michigan for years. We each had Wills in Michigan.
Every state has unique legal requirements for Wills and medical directives.
Generally, if your Will was valid in Michigan it will be valid in Texas. You want one that uses state law to distribute your estate efficiently. Efficiency means speed and low cost. The Texas probate system is one of the best in the country, and was used as a model in several other states. To take advantage of all the system's efficiencies, your Will should be adjusted under Texas law.