Really I like GA and it sure brings a unified treatment for geometric calculations, but in these tutorials I would very much like to see examples of something quaternions can not do, e.g. involving exterior algebra, subspace intersections, duality etc.
However if you want to see the quaternions as a vector subspace in problems of higher dimensions or in non-euclidean manifolds, for example path interpolation, finding integral solutions or representations, they fall short and it makes sense to use a Clifford algebra that is compatible with differential operations (e.g Lie) and gives consistent calculations across all dimensions.
When people limit themselves to Gibbs-style vectors or to quaternions as a primary formalism what they are doing is pretending that vectors and bivectors are the same kind of object, and this pretense leads to massive amounts of confusion. cf. https://en.wikipedia.org/wiki/Pseudovector
The biggest thing GA adds compared to quaternions is that the same technology generalizes to higher or lower dimensions and to pseudo-Euclidean spaces (and to generalized Möbius transformations, non-metrical contexts, to modeling points and circles as multivectors, etc.), and there are many vector identities which are awkward to express when you are pretending that vectors and bivectors are the same.
Another advantage is that you don’t need any arbitrary conventional rules about multiplication of {i, j, k}, since typically the basis is specified in terms of orthonormal unit vectors e.g. e₁, e₂, e₃, so that it becomes very obvious how basic bivectors e₁e₂, e₂e₃, e₃e₁ should multiply: (e₁e₂)(e₂e₃) = e₁e₃ = −e₃e₁, etc.
How do you get a geometric algebra without at least a pseudo-Riemannian metric?
My point is that these advantages are seldom (if at all) discussed in most online introductions to GA I've read so far, yet to me they're the real selling points of GA.