The only time that it really matters if you are on 421/421 or 21/22 is if you are going beyond San Antonio either way. (Example: Austin to Tuscon or El Paso to Dallas.)
If you were to book 21 connecting to 1 or 2 connecting to 22, you must disembark in San Antonio for an overnight stay (in the far from luxurious station) and wait for the general boarding of the new train. If you were to book on421/422 all the way through, you could sleep in your seat or room all night through the stop!
If your sleeper is 2119/2219 (I think), it is the trans-dorm - which is not put on/off the SL. If you're sleeper is 2120/2220, it's the full sleeper on non-SL days that just go CHI-SAS. If you're sleeper is 2130/2230, it's the full sleeper that goes CHI-LAX, and is switched in SAS between trains.
The full sleeper has Bedrooms A-E and Roomettes 2-14. The trans-dorm only has Roomettes numbered above #17. (It has no bedrooms.)
Edited by the_traveler, 21 March 2017 - 11:30 AM.
Take it easy .......
Take the train instead and enjoy the ride!