I've only heard great things about the Kabuki Trap Bar. Same w/Prime's Trap bar. Eleiko also has a Trap bar but I haven't seen as many reviews as I believe it's even more expensive than the other two and that's really the only complaint I hear about all three; the price tag. Now, the Transformer Bar I have heard mixed reviews but more good than bad. I just had a Microdiscectomy on my lower back and I'm wondering if I'll ever be able to Barbell Squat and DL ever again without immense pain. I'm really wondering if the Marrs Bar deserves the hype.
Never used the Marrs but heard great stuff from people I respect a lot. Seems like primary is that it provides a low bar squat without stress on the shoulders. Not sure how important that is to you but lots of older PL guys love it for this aspect.