The following things change when you swap between the FR vs. RR layout:
- The weight balance changes, which influences traction.
- The weight is placed further to or away from the centre of the car, changing the rotational inertia of the car.
- The suspension arm tends to flex differently (decreasing anti-squat with FR as the shock resists upward movement at the front, increasing it with RR as the shock resists this at the rear).
- The amount of usable setup holes changes (due to gearbox clearance).
- The shape (cutout) of the wing.
- The protection of the shock.
If you ask me, it's a matter of preference:
- The RR layout in a subtle way works like a rear-mounted weight or rear motor car: You might find slightly more traction, but once sliding/oversteering, it may be slightly harder to correct. I have heard the RR can help on carpet to increase steering.
- The FR layout places the weight further forward and closer together the CoG. The first may result in slightly less grip, but the latter may help you to correct the car more easily - in fact it may feel slightly more lightfooted (nimble, quick to react).
- Besides the handling, it also influences your access to the dampers, the protection of the dampers and the amount of holes available on the shock tower (where I must note that the inside 3 holes give a very progressive shock setting, I'd say you might use them if you drive on flat/smooth surfaces and high bite, but with a lot of bumps the more upright settings will have the preference).
I'd advise you just to try them both if/when you've got a car that feels somewhat dialled (the differences are not night and day, so don't use it to try and transform your car's handling). If you don't want to bother with trying them back to back, ask yourself what you find the better position for the shocks based on the practical considerations
