Do the vas deferens carry urine or seminal fluid or both?
Vas deferens carries seminal fluid only.
The vas deferens is an approximately 18cm long tube that commences from ductus epididymis and ends in ejaculatory duct. It carries seminal fluid from epididymis to ejaculatory duct. Ejaculatory duct opens into urethra. Male urethra (unlike female urethra) carries both seminal fluid and urine.
The commencement of vas deferens from epididymis :
Diagram of male reproductive system : see the vas (ductus) deferns starting from epididymis ending in ejaculatory duct in prostate gland. On the other hand, urine flows from bladder to urethra.