i suppose if you want to lower and maintain performance, Swift springs is the way to go, per the thousands of fans out there.
tein is overrated imho. i was one of the first ones to have TypeHA coilovers in the usa back in the late 1990s. was a fan back then, but today, im more of a Swift fan if im lowering my ride. matched with stock dampers, paint does not crack off, almost oem like durability.
for me though, i prefer stock ride on my Z. just front stabilizer and the wheels/tires is all it took.