A spring is a spring is a spring, they are all made from stainless steel so should all be of similar quality. Most have plastic buckles, which I dont really like but some eg XS Scuba and DGX use steel buckles. The thing to be careful of is making sure if you decide to go for a third part spring that the buckle will fit your fin posts. They are not all the same size. The XS Scuba/DGX straps come with two buckle sizes so likely you'd be fine but having never seem the Apollo posts I cannot be 100%. You also need to be careful to ensure you get the correct spring length. A good approximation can be had by donning boots and fins and then use a piece of string and measure around your heel from just before the post to just before the other post, if you then measure string and subtract around 2-3cms this will give you a "rough" idea as to required spring length. Buying the Apollo spring might be easier as they come in 4 sizes, 22.5, 25, 27.5 and 30cms, if you get wrong size it might be easier to exchange. Good luck.
---------- Post added February 27th, 2015 at 10:35 AM ----------
I've bought several different sized Apollo springs only (25 & 27.5) to use on other fins from memory they are slightly smaller diameter wise but quality wise see the same as others.
---------- Post added February 27th, 2015 at 04:53 PM ----------
I just realized that unless Apollo have come out with a different spring strap or an additional buckle version, using the Apollo springs will mean that you will have to cut the posts off your fins as the straps screw onto the fin. If course once you do that there is no going back. I put some Apollo straps and some Cressi fins many years ago and did feel kinda nervous cutting posts off. If you are not comfortable performing this surgery your self you'll need to either get a shop to do it for you or go with third party straps that use the post and buckle.