It's a wise first purchase. Stick to these kinds of generic low premium bars if your strategy is to stack to the sky. You are spoiled for choice in the States. We can't get stacker bars at such a low premium in Australia.
Try to have a good idea of why you stack. Keep in mind that the spot price of precious metals may be suppressed for years or decades to come....no one knows for sure. If you are also a collector or develop collector tastes as quite a number of stackers have and do, then on the one hand, you don't have to worry about spot price movement and which blob is better (all blobs (generic junk silver) are equal because they are merely fodder for the melting pot in the end). Mostly you just buy what you like. If you are buying collector products (coins, medals, rounds, art bars, statues, etc) to be able to sell and turn a profit some day, then it's important to try to understand he market. This can be very challenging and maybe takes quite a while to get good at picking more winners than snoozers. .
I don't think they differ much if not concidering the logos or price. Did you check other bars prices after the purchase?
People seem to love the stacker bars. We have some old AMARK ones (1oz and 10oz) but none of the Scottsdale or APMEX ones yet. I don't typically like anything APMEX branded but I do like the look of the recent APMEX RMC 100 bar, I'd just want it in kilo or 500g size. This APMEX stacker looks like a good first buy to me!