There are many articles about the disadvantages of spaying. Overall, on average bitches gain 9 months of life when spayed and usually die of a tumor, rather then trauma when intact.
Intact bitches age later than spayed, keep higher cognition levels, lower lesion risk, and incontinence comes 'only' by degeneration of spinal cord, (incontinence rises 3000%, which has to be treated by restoring the hormones $$)
However you must note, mammary cancer incidence is high if she has more than 2-3 heats, (50% are malignant) surgery is not costly nor complex.
Hypometra is a real death risk, rarely fixable without spaying and it's a risky surgery. Incidence is high...
Spaying comes in variety of forms:
ovariohysterectomy - removal o all organs, the usual
hysterectomy - removal o uterus, a solution against pyometra
ovariectomy - removal of ovaries, nonsense.. used in laparoscopy spaying, as it reduces post-op complications
There is another, that just cuts the fallopians but doesn't bring health advantages (don't know the name)