Hi Nic. You're right, there are sooo many brands to choose from these days. Like Christy said, I'd stick to the bigger brand names. The companies do a lot more R&D on their products and the products use the newest and safest chemicals/drugs.

With the online stores the thing you have to be concerned about is how they store their product. There was an article in one of the vet publications recently that found that a lot of online stores keep all their stock in big warehouses that are not temperature controlled, and that if the temperature in the warehouses gets too high it inactivates the product. So yes, the spend a lot less, but you also get a product that no longer works at all.

The most common products I use on my dog are either Sentinel Spectrum (is a tablet that sterilises adult fleas and kills all the nasty worms, including tapeworm and heartworm), or I just use something like a drontal chew (for the gut worms) and either frontline or advantage for fleas. Luckily heartworm is extremely low risk in my area so I don't have to be too worried about that little nasty.