I'm still wondering...(and maybe just way off base/clueless to your point)...your gonna use them to watch current draw on each phase. This is dependent on when your aware. I'm thinking spend your money on a clamp on portable as its just something you want to check every now and then or when your experiencing issues?
I carry... in top of my toolbox
DVM - Fluke 23III Multimeter ->
http://www.colorado.edu/physics/phys...cs/Fluke77.pdf
IR Thermometer -
http://download.sears.com/own/03450466e.pdf
Yokogawa Model 300 -
http://www.yokogawa.com/rd/pdf/TR/rd-tr-r00031-008.pdf
These allow me to check many things beyond an isolated static install location as well as my stick home or others...