Random opinion. Highly debatable. but very much defendable too...
In test cricket, because of the nature of the game, the slip cordon is populated by the primary fielders. leaving the off side open, the bowlers temp the batters to drive and edge to slips. the main wicket taking strategy in this format is, therefore, very much dependent on slip catching.
In ODI cricket, because quick runs are paramount, the inner circle of fielders assumes greater importance. Not just to take catches and cut runs. But also to effect run outs with direct hits, and more importantly, create the fear of sharp run outs and reduce sharp singles (and reduce rotation of strike, drop the scoring rate) and even cause run outs out of confusion. Two gun fielders in the circle will mean a world of difference. three would be an army. I don't know how to quantify their contribution. But for the bowling attack, such protection is invaluable in building pressure and bagging wickets.