
If you use the drug to stop seasons your very likely to end up with Pyometra or some other issue needing a spay.
Assuming your bitch is fully mature (has had two or three seasons) and not going to be bred from then spaying is probably the better option.
Of course you could simply keep her as nature intended (and deal with seasons, adn keepign ehr safe from being mated) and be vigilant about looking for signs of Pyometra as she gets older, accepting that you have about a 30% chance she may need an emergency spay.
Something also to take into account is if she is of a breed that suffers huge coat changes making grooming difficult and unpleasant (Spaniels come to mind), this may decide you in favour of keeping her entire.
There is also the issue of Mammary tumours, more common in some breeds and lines than others, but overall around 40% of bitches will get them, and around half of them are malignant. Vigilance means if you get them treated when small the prognosis is excellent for curing the problem.
This article sets out the pros and cons rather well
http://www.naiaonline.org/pdfs/LongTermHealthEffectsOfSpayNeuterInDogs.pdfAs for worry over the surgery, no surgery is without risk, but operating on a young fit animal is preferable and with modern anasthesia, with such routine surgery, a minimal risk.