If you are wanting max effect of bacteria, cycle out of the two. Stresszyme (which is not really a 'zyme, but anyways...), is more about reducing stress for certain instances, AloeVera being one of the ingredients if I'm correct, -this is kind of okay, but if you've got a fish with potential gill problems the coating that stresszyme gives may exacerbate the problem. I know cycle is pricey, but it's worth it. (btw, if you already have a cycled tank, ignore what they say on the pack, you don't need to use it every time you do a water change, but it is good, if you're cleaning out your filter and want to make up for the bacteria you've lost during the change)
Some people may swear by it, but I reckon, in Melb, we don't really need it... when I do water changes, I just use aquaplus and salts. and to be honest, the salts I use already has Na thiosulphate in it, so using aquaplus, may be a bit of over-kill. I just use it coz I mix the salts with the water immediately before I introduce it into the tanks (don't have enough room for a holding tank with which to pre-mix/aerate water before adding it to tanks during water changes)....
Sorry, hope I wasn't jumping the gun too much there/going offf in some crazy tangent....