There are almost definitely a priori reasons to think a 1500% one is much riskier. 20% is in the realm of possibility considering you could get ~15% yields from

There are almost definitely a priori reasons to think a 1500% one is much riskier. 20% is in the realm of possibility considering you could get ~15% yields from crypto.com, there were also some powerful players with deep pockets funding anchor paying the difference, and that there was almost 20bn$ TVL. Stablegains had nothing going for it, in fact it had all of the risk with none of the reward. 1500% APYs are usually attached to LPs carrying huge risks of impermanent loss rather than stablecoin staking and are usually very transient in that they evaporate within hours. FWIW I disagree with Anchor being termed a ponzi.