BASE OR SIDE MOUNTING
Base-mounting works well on road seats like the aftermarket recliners because it means a sliding subframe can be used to adjust the seat back and forth. In motorsport applications this is not permitted, and by mounting the seat by its sides rather than the base provides a stronger, more rigid mounting point (as the seat is effectively sunk into the mounting points rather than sat on top of it), and it also allows the seat to be mounted much lower than a base-mounted seat, which is good for giving the driver plenty of space, especially headroom whilst wearing a crash helmet, and helps keeps the weight and centre of gravity lower too.
On side-mounted seats the seat mounts themselves also play a crucial part in driver safety, not just by securely holding the seat where it should be but by actually strategically deforming to slow down the impact and absorb some of the energy being transferred to the driver.
Most aftermarket bucket seats are side mounted for increased strength