I can only find Tetra Pond Aquasafe, so I will assume this is what you mean by "Pond Safe." It seems to be much the same as the regular AquaSafe, though they do not list ingredients, but it performs much of the same tasks. Odd that they should be priced differently, but maybe that is just because the "pond" bottle is larger so per volume it is less expensive? Most conditioners are similar. I buy the 2 liter jug of the one I use, which happens to be API's Tap Water Conditioner.
One has to be careful of the ingredients, as some of these products add things like aloe vera which has no real benefit but has been shown to affect fish gills. The other thing to watch is how much you need per volume. Having to use more of a less expensive product may not be less expensive than using less of a more expensive product, plus you want to use less for the sake of the fish. All of these substances added to water get inside fish, and the less the better.
I use the same dechlorinator as Byron (API Tap water Conditioner) and the dose rate for that is 10 drops in 10 gallons*. It also has the advantage that it does not contain aloe vera or anything else which "promotes the slime coat"
*Although if your water provider uses chloramine rather than chlorine the dose rate is 30 drops in 10 gallons.
Agree. To compare the two, with the API I use 1 ml to treat 20 gallons, so 0.5 ml treats 10 gallons, or one drop per gallon using a dropper which is more convenient in smaller tanks.
Compared to 2.5 ml for 10 gallons...you can see that you use five times more for the same volume of water. That is more chemical getting inside the fish, and if you worked out the math it might come out more expensive than the API long-term.
API Tap Water Conditioner is more concentrated, with 1 ml treating 20 gallons compared to Prime's 10 gallons [dealing with chlorine here]. But there is another issue with Prime, and that is what it does beyond dechlorination. The ammonia, nitrite and nitrate detoxification (Seachem even cannot fully explain how the latter works, and this always bothers me when I use such a product with live fish) is normally not something you want in a healthy and balanced aquarium. New tanks, yes; but once cycled, not the best product. And the detoxification of ammonia, nitrite and nitrate is only temporary, roughly 24-36 hours according to Seachem, after which is again becomes toxic if still present.
The problem with prime is 1) they don't say what's in it and 2) if it does everything they say it does it must be full of chemicals. But it can be useful during fish-in cycling as it does temporarily detoxify both ammonia and nitrite.
API Tap Water Conditioner contains only sodium thiosulfate (to remove chlorine) and tetra sodium EDTA (to bind metals). Info from API product data sheet. Like Byron, the fewer chemicals I add to the tank the happier I am. I am not prepared to use prime until they say exactly what it contains - and I'd probably be even less likely to use if they did say.