Determination of products in reactions involving carbocation rearrangement?
All else equal, the smaller group migrates preferientially. The energy required to more the group is related to the mass of the group:

$$W=\int_0^\vec{x}\vec{F}\cdot d\vec{x}$$
$$\frac{d\vec{x}}{dt}=\vec{v}   \ \ \ \ \ \therefore \ \ \ \ \ d\vec{x}=\vec{v}dt$$
$$W=\int_0^t\left(\vec{F}\cdot \vec{v}\right)dt
$$$$\vec{F}=m\vec{a}$$
$$W=m\int_o^t \left(\vec{a}\cdot\vec{v}\right)dt=m\int\left(\vec{v}\cdot\vec{a}dt\right)$$
$$\vec{a}=\frac{d\vec{v}}{dt}$$
$$\vec{a}dt=d\vec{v}$$
$$W=m\int_0^\vec{v}\vec{v}\cdot d\vec{v}=\frac{1}{2}m\vec{v}^2\vert_0^\vec{v}=\frac{1}{2}m\vec{v}^2$$