Yes, the SX androids are cheaper (ESP SX4 since you don't need a AI Persona core) Their are 2 main reasons I like the SX androids -

1) if you slot a VX3 Chip into some one, they can control 3 SX androids at one time, which basically means you can have your lvl 20 pawn do 3x the work.

2) once you start uploading pawns into the Skycore, you can have them connect to SX bodies to keep doing stuff around the base.
The main downside to SX androids is the SX virus event, which even with a huge stack of security servers, some how always knocks out 1 or 2 of them. Also, depending on if you have a mode for EMI shielding, solar flares will knock out all the SX androids as well, and they cannot travel too far from your base on the world map, as they loose connections strength, so it's a good idea to keep a few meatbags and/or normal androids around base.