If you can find it, "The Design of Broad-Band VLF Receivers with Air-Core Loop Antennas" by Evans Paschal is a good reference, if slightly dated. It describes in detail the design of the Stanford VLF group's research receiver.
Basically, if you have the space and $$ for copper, you want a B-field (loop) receiver. Paschal shows that the overall receive sensitivity is proportional to the mass of copper in the loop.
High impedance E-field receivers are useful mainly for portable work. Paul Nicholson (
http://abelian.org/) wrote some antenna modeling software for VLF that you can use to find an equivalent circuit, basically a pure capacitance for an E-field probe. He was involved in the first transatlantic amateur communication at 9 kHz.
Propagation at VLF maintains phase coherence over long integration times, so you really can trade off TX power and communication rate to a fairly astonishing degree, given GPS-locked frequency standards at both ends. This is fortunate, as it's difficult to get more than microwatts ERP at VLF, unless you're the military