Well... SCPH-1150 is the prototype pad for the SCPH-1200 that never quite made it, so it may not always work quite as well, and certainly it never seems to be useful over choosing SCPH-1200. So that part is at least answered for you... stay away from SCPH-1150...
As for the main problem... have you tried updating your adapter drivers, or at least using different ones (if you're using Microsoft drivers, try the manufacturer's drivers, and vice-versa). Is your DirectX installation up to date? Also, if you have rumble enabled, disabling may fix the problem too (pSX is still a little touchy about some controllers/adapters and rumble).