Experts and BHG readers answer.
I am going to assume that you have an older shower. Whether you have two handles or one is a personal preference. In most states the building code now requires you to have an anti-scaling mixing value and many homeowners choose to go with a single handle option like the Symmons Temptrol system. If you do have an older house with out an anti-scald mixing value they can be installed fairly easily even if you have a tiled shower by a professional plumber.