I imagine this will start a holy war, but my preference is adjustable struts (like Firm Feel) without heim joints, and rubber strut bushings. I have tried to be open minded about the benefit of heim joint struts, but have not gotten a good technical response from any of technical people I've talked to at 4 companies that sell them. So maybe somebody here can clear this up for me. The heim joint length makes the effective strut radius to the LCA shorter than stock, because the strut now rotates from the heim joint rather than from the K-member. As the LCA goes up and down, the struts push/pull sideways on the bottom of the LCAs because the distance from the bottom of the LCA to the heim joint changes, and the strut is a fixed length, aside from strut bushing give. The shorter the strut radius, the farther will be the sideways push/pull per vertcal distance of LCA movement. The original equipment, softer strut bushings allow some compliance to reduce that movement, but the stiffer bushings don't have much give. So, more push/pull from shorter strut radius, plus less bushing give, impedes LCA vertical freedom of movement and increases the amount of movement at the bottom of the LCA. Stiffer strut bushings probably give better steering wheel control when going over potholes and bumps than do the original factory bushing, but that could be achieved by stiffer strut bushings alone, without the heim joints.
Separate issue, heim joint struts and stiff bushings are wrong for drag racing, because they will hinder the unsprung weight from falling at launch.