Both will control vehicle motions well, but I have read that Konis have a harsher ride compared to the Bilsteins.
On my class C (E450 chassis) I got a good alignment, installed big Hellwig swaybars, and installed a Saf-T-Plus steering stabilizer. These made a very significant difference in the driveability and stability of the RV. I then installed Bilstein HD shocks, which didn't make as big a difference, but got rid of the wallowy feeling over undulating roads and improved the ride a bit.
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