....a long explanation, but a needed one.
One of the most important characteristics of a mixer is its ability to
handle large input signals without overloading. if overloaded by an
unwanted signal, chances are that it will not be able to handle the
weak signal you're interested in. the physical mechanism involved is
not important, except for the fact that increasing current through an
active mixer (re FET or transistor, or the injection power in a DBM
tend to alleviate the problem in some measure. the nois figure of both
is more or less equal and adequate in the HF range. the main advantage
of the dual gate MOSFET is that it needs much less power from the local
oscillator and can save you an amplifying stage. Not really crushing,
but sometimes neeedful.
If you're talking about a simple first receive I'd go with the MOSFET
mixer. there are very good examples in the hand book. iI used them for
years with success and still using them in one form or another.
the problem is much less severe at the second mixer, because the IF
filters tend to defend it from large unwanted signals and the amplituse
variations are also smaller due to AGC action.
Soooo , KISS (keep it simple, stupid!!!), a very good adage. goood luck
with your first.
Saandy 4Z5KS