Hallo Mahmood,

there are same disadvantages with pure sensor tracking. Are you expecting to have clouds travelling across sky? This can heavily interfere sensor electronics. Just if you have set a certain threshold for signal. I have seen poor systems, coming completely out of control, when there are some clouds in the sky. It's just the change of bright sky versus cloud what can make trouble.
If on the other hand sky clouds are leading to very diffuse sunlight, pure sensor controlled tracking may allways look for the brightest angle in the sky, and tracking motors are allways running...
Another point: If you have some dirt on your sensor, like bird's droppings, 'tree droppings', sand a.s.o. sensor tracking can also completely fail.
So, I would recommend some math tracking with fixed, calender dependent controlling.
Mounting solar system like a telescope may become to expensive. Telescope tracking has to be much more precisely, because when making a photo telesope has to be controlled very carefully over minutes and possibly hours. If there is only very little deviation from exact positioning photo will become a big mistake.
Because tracking of telescope has to be very precisly, its a big advantage when only ONE axis has to be controlled. But this high precision is not needable for solar system tracking, isn't it? So, I would take mounting that is least costing. Two motors you need anyway, means you cannot save costs for additional motor when having equatorial mounting.

Bye,
Kai