So the "question" now might be:

is it better to have to different chains, i.e. bitcoin and rootstock, with the second being a superset, in terms of functionalities, of the first, or is it best to just have the second (so just ethereum)?

I tend to think that is better to split them, but I don't have any real evidence to support that assertion.

Some thoughts however:
pros (for splitting): two different chains can be tweaked differently (e.g. block time) to achieve different objectives.
cons (for splitting): one single chain is easier to mantain, to debug, to develop, to upgrade compared to two (this may be a strong cons).

What do you guys think however?