Nah… They serve different purposes. Depending upon your needs one is definitely going to work better than the other.
A great example is all of the ecommerce options. Webflow has a native option that is out of beta, but it serves a purpose that the other solutions do not (and vice-versa).
For all the ideas discussed above, Memberstack is the better choice. If you have different needs, Webflow’s native Memberships may be better (once it’s out of beta).