Welcome to the pets stack exchange.
I'm sorry to hear about your dog but you are right in thinking that there is more to spaying than just stopping their reproductive capacities.
Advantages:
- No seasons - No blood discharge to clean up
- No ovarian cancer - No ovaries, no cancer.
- Doesn’t Contribute to Pet Overpopulation – There are already so many unwanted dogs and unfortunately, not spaying can increases the chance of yet more dogs adding to the list.
Disadvantages:
- Anesthesia Side Effects – Spaying requires anesthesia.Although only 1 in 5 dogs are negatively affected by anesthesia it can still be life threatening.
- Spaying may increase the occurrence of urinary
tract infections, urinary incontinence, and hypothyroidism.
- Possible Weight Gain – Your dog may be less active, so they may put
on a few pounds. This can be managed with diet and exercise
The main concern is actually the age that you spay your dog. It is not recommended that you spay your dog under 1 year old as the hormone estrogen, which is no longer produced in spayed or neutered dogs, plays a crucial role in bone growth and development. The removal of estrogen-producing organs in immature dogs can cause growth plates to remain open. The dogs continue to grow and wind up with abnormal growth patterns and bone structure, which can result in irregular body proportions. This also means that in later life dogs that have been spayed early are more likely to have hip dysplasia, cranial cruciate ligament tear and elbow dysplasia in later life.
It is important to note that research on Spaying and Neutering animals is still on-going. It is completely up to you as the owner to decide for your pet whether or not s/he should be spayed or neutered. Don't beat yourself up over her passing as most of the time pyometra is not fatal. You were simply unfortunate.
The argument for spaying/neutering is constantly being debated. From a personal standpoint I prefer to spay/neuter as it has clamed my dogs down both sexually and emotionally. Side note: I've owned dogs all my life and currently live with eight who have all been spayed and neutered.
Edit:
As for the 1 in 5 dogs are negatively affected by anesthesia. This is in regard to any reaction. This could be a bump on the skin/Rash etc.
For some more information you can look here:
How safe is anethesia for your pet -Comes with some nice statistics on a relatively large study of dogs. Including factors that could add risk.
Top 10 reasons to spay/neuter your pet
Current perspectives on the optimal age to spay/castrate dogs and cats
Long-Term Health Effects of Neutering and Spaying Dogs.