I agree with your statement.
Every gambling website has their respective bonuses and rewards that they give to their customers. While you may compare their bonuses with one another, there will always be one aspect that the other gambling website is better than the other. No matter how you compare, it also boils down to the preference of the person on which he/she wants to gambles.
A customer who has been betting for years in Stake might choose this gambling platform even if Bitsler may have better rewards due to personal preference and attachment. Even if you try to compare their rewards, everything revolves around the choice of a person on where he/she wants to gamble.
Doesnt matter if you do see some similarities or differences despite on having the same owner.They are marketing different and its up to them whether they would just be closing the another one or have both.
Its their business then its their right whether on what decisions they would really be taking but pretty much sure that we are aware about the differences among the two.