The Dignitas preparation is 15 grams of pentobarbital in 50 ml of water.
The brand that A sells, Pisabental, is 6.3 grams of pentobarbital in 100 ml of carrier liquid. From researching other veterinary pentobarbital formulations, it's probably a combination of water, alcohol, and propylene glycol. So 2 bottles is 12.6 grams of pentobarbital in 200 ml of liquid.
As far as we know, no one has volunteered to do a taste-test of both. lol
They both taste like crap; we all know that. The Dignitas preparation tastes worse because it's more concentrated, but there's less to drink.
If you do a search for "Pisabental," you'll find numerous reports of people who successfully used it to CTB. There are even people who drank it without anti-emetics.
N tastes like crap. That's just the way it is. For some people, that's going to be a deal-breaker, and they'll need to use a different method or stick it up their butt.