If you have to use a topical then Revolution is the safest although it is not the most effective.  The active drug in Revolution is selamectin which is very closely related to the ivermectin in Heartgard (both are actually macrolide antibiotics).  Revolution works okay against fleas but in my experience isn't that great against ticks.  It is the product I use on cats and on exotics (rabbits, ferrets, hedgehogs) because it is so safe.

Frontline works very well against fleas, flea eggs, and ticks but does leave a greasy spot for a few days but overall it is pretty safe.  The chemicals in Frontline only work against the nervous system of insects so it is pretty non-toxic for mammals.  I am not a fan of Advantix because although it works well it does so because the company added pyrethrin to their regular Advantage product.  Pyrethrin is a pesticide and if you accidentally put this product on a cat it can cause seizures and death so we stopped carrying it at our clinic.

Heartworm is not a big problem here in the Northwest but I do give my dogs Heartgard monthly (mostly for deworming).  I have changed to Comfortis for flea control when needed because it is a plant-based pill so no oily mess!  It does not do ticks or heartworms but it does kill fleas the fastest (within 30 minutes).  Side effects are rare but can include vomiting and you should not use it if your dog is taking high-dose ivermectin for demodectic mange (the lower dose in Heartgard is okay).

So it really depends on what part of the country you are in and risk for heartworm, fleas, or ticks.

Pam

SE Texas is heartworm haven, dogs here are on preventive from puppyhood until their last day.  Trouble has been on the Heartgard that is a tablet – non flavored (because of allergies) for many years.  I suspected years ago the Frontline was causing some allergy reaction as well.  While she does have flea allergies, she is in the house almost constantly, and we have been good without it for many years. 

Last summer, I had some concern with ticks – found a couple on her at various points.  Our vet is 'reserved' about introducing anything that is not absolutely necessary.  He has kept her on heartworm preventive, but did not want to use a flea/tick preventive unless they ticks were bad enough to cause a health concern of their own.  He also has not given Trouble vaccinations of any kind since her surgery.  I carry a letter with me stating she is healthy, but under veterinary care for cancer and to contact them if there are concerns about her vaccination status.