On the OEM system, half-shaft axles and the wheels are one unit. So, if the half-shaft axle breaks the wheel/broken axle can, and does, come out of the axle tube and pass you when you're least expecting it. In short, the wheel falls off. Is this a problem on the highway when you are not off road? Well, yes, the axle will break more often under off-road stresses, however, it only takes one occurance on or off road to become a believer in full-floaters!
On a Full-Floater system the half-shafts and wheels are separated. There is a spline that moves into the wheel and engages the axle to the wheel. Now if the half-shaft axle breaks the wheel cannot loose itself from the axle housing. This is a very positive thing. Four wheels on the ground is a lot better than three wheels on the ground and one additonal wheel "on the ground," so to speak.....
There is also an argument of weight distribution of the Jeep to the to the axle tube ... but I won't get into that one...For Towing, it's a great! Drivability sould not be affected. Is the upgrade worth the money? It's your choice.