You have asked the question of them month. Both are very nice units.
To decide which one you want, you need to decide what you want it to do for you and how you plan to use it, and what will you want in the future.
The PLX is a very nice unit and its box makes it easier for hard mounting if you plan to have it and leave it installed in your truck. I have one in each of my trucks mounted in the glove box. Some of our customers have mounted them in their dash so they are visable all the time. It works very nicely in this role.
For tuning, the LM-1 form Innovate is a very high end unit with incredible expandibility. It has data logging ability as a stand alone unit, and has all kinds of expansion add ons. The new AuxBox will allow you to data log all kinds of things like manifold pressure, AFR, RPM, injector duty cycle, EGT, induction air temp, and on and on. It also has a built in accelerometer so when you combine the LM-1 with the AuxBox you have pretty much your own real road dyno. They are also coming out with an extensive gauge line that will all run off of the AuxBox and LM-1.
When tuning my preference is the LM-1, but the PLX is great for a simple hard mount unit.
Anyway, either way you go, you are making a good choice.
Gadget
www.GadgetOnline.com