I read for hours and hours on the subject. You reach a point where you think yep that's the one for me but read a bit further and other opinions tend to make you change your mind.
Those who say the Kinugawa is better than Mamba don't say why. I see a lot of similarities so, for me, it's either toss a coin or go for the one that will be easier to fit.
Either way, everyone agrees that both are way better than the HT18 so I doubt I'll be disappointed. My HT18 goes reasonably well with my auto trans so any improvement is a win.