Agree w/tamc91. We have a small motorhome and we never stay at RV parks with the exception of the one at High Island (no state parks nearby). State parks just have more to do, and are more scenic as well. Fishing, boating/kayaking/canoeing, hiking, wildlife observation/photography can be done at the majority of SP's. Some even have swimming pools (Bastrop SP) and golf courses (Lockhart SP). Most RV sites at TX SP's don't have sewer hook-up's, but all parks with RV hook-up's will have a dump station.
Be aware that the more popular parks such as Brazos Bend, Inks Lake, Garner, Pedernales, McKinney Falls fill up extremely quickly. However, you can go to the SP website and make reservations many months in advance.
We like Martin Dies SP as it is often much less busy at times when other parks are full. Also like Sea Rim, Meridian, and Ft. Parker as they are smaller parks with fewer campsites, so you aren't camping with a hundreds of other people. We do not like Lake Livingston SP as the campsites are extremely close together.
At some point you will also have to check out the SP's in Arkansas. They spend a lot of money on their parks, and most of them have extremely nice facilities.