I have run them all, and I will say this.
The REK lower is a nice unit, i've had no real trouble with the material it is made of, except maybe a little skeg flex. The lower does cause more lift for one reason or another, but its manageable. Its light also.
The Lawless is a VERY nice product, many people use it successfully. Its not cheap, but you do get a very nice product for the money. It has the narrowest frontal area of any of the lowers Ive seen or used. Its also fairly light, and Fred now offers it tapped to accept the OS propshaft which has proven to be bullet proof. He also offers it with or without the holes at the bottom near the prop shaft housing.
The OS lower is also a very nice unit. I am in the process of mounting my Rossi to it for some testing and will know very soon how it works. A couple guys have already done this.
Another unit that we are looking into is the Hyper Prod CNC "Angle-Drive" Not much info on this one, but?
~James