Nothing wrong with I-10 in my opinion. We like Sonora and Fort Stockton for RV parks on I-10. I-10 has plenty of nice rest areas and has a little less likelihood of hitting a deer along the way.
Deer strikes are a real possibility anywhere in west TX but the stretch from San Antonio to Sierra Blanca, on any route, is higher around dusk and dawn. We generally do not drive during those hours unless we have to.
US 90 is fine if you like small towns and two lane roads, and border patrol check points. Fuel stops need a little more prior planning on US 90 west of Del Rio. Sanderson is a good stop for fuel and has RV parks too. There is a by-pass around Del Rio that will miss most of the town including the Wal Mart. I personally do not not like the in and out at Wal Mart but then I am pulling a 30ft 5er and need diesel which is only available at the end pumps. Del Rio is a good place to do some cross border shopping and buy any supplies you need before reaching El Paso or Las Cruces.
Fort Davis is a good place to visit and is a more interesting route back to I-10 than the stretch of US 90 from Marfa to Van Horn. IMO