Koni FSD and Sports with oem Sport springs and Koni Sports with BMW PS springs and bumpstops. The best of those for ride quality was probably oem sport springs with Koni Sports.
There's just more compression travel with KW SC prior to bumpstop contact than any of those spring/shock combos. The springs are stiffer so the car follows road irregularities more but bumps are absorbed by the suspension more so than being transmitted to the chassis. BMW uses bumpstops as a secondary spring whereas KW uses them to prevent the dampers from bottoming. But if you lower the car too much with KW you'll lose that extra compression travel and ride quality will get harsh as it does with lowering spring/shock combos.
2007 E90 335i, TiAg, 6AT, ZPP, ZSP, ZCW, 6FL, HD
Quaife lsd, ETS fmic, GIAC s/w, Dinan intake/exhaust/oc, Koni/M3 susp, Apex Arc 8, Mich PSS