Unless you tow a bunch of different cars I give 'em both a resounding thumbs down.
Story elsewhere on the forums in a Tire Pressure Monitor thread. about a man who noticed the tires on his towed heating up..
Every time you tow you have to install those systems (Both of 'em) and this means there is a chance to make a mistake.. That is what happened, he made a mistake, had the TPMS not caught it, he could have either had to do a brake job when he got where he was going, or he might have had a towed fire.
I have spoken to folks who, when towing a short distance (Say to the dealer), OH, forget it, too much trouble for this short tow.
I much prefer an installed system, Bolted in once, and then to tow you just plug in a cord or two... Way better in my not at all humble opinion, It is always there,, and if the original install is done right (mine was not, but I fixed it,,,, after a brake job,,,,) then all you need do is hook up the control cord a few seconds, so no temptation to "oh forget it" for a short tow. Like when I towed the car a mile up to PEP boys for a new fuel pump.
Home is where I park it!