IRS vs. 4-link, aka: RS vs DSE...

[Rhino]

I've not seen either setup in person, but may provide at least a little info.

You'll likely be using coilovers on both setups, so springrate/shock changes would be possible either way.

The advantages you're getting with IRS is the ability to bake in static camber, and realize camber gain through suspension travel. Both of which are utilized to compensate for body roll.
The disadvanges are added cost/complexity.

If you're looking for a compliant ride 90% of the time I would venture a guess that you wouldn't realize a measurable advantage 95% of the time.

You just have to determine if that added cost/complexity is worth it for the 5% of time it would benefit you.