  Particle and nuclear physics are moving toward a new generation of
experiments to stress-test the Standard Model (SM), search for novel degrees of
freedom, and comprehensively map the internal structure of hadrons. Due to the
complex nature of QCD and wide array of past, present, and possible future
experiments, measurements taken at these next-generation facilities will
inhabit an expansive space of high-energy data. Maximizing the impact of each
future collider program will depend on identifying its place within this
sprawling landscape. As an initial exploration, we use the recently-developed
PDFSense framework to assess the PDF sensitivity of two future high-energy
facilities --- the high-luminosity upgrade to the LHC (HL-LHC) and the Large
Hadron-electron Collider (LHeC) proposal --- as well as the electron-ion
collider (EIC) proposed to map the few-GeV quark-hadron transition region. We
report that each of these experimental facilities occupies a unique place in
the kinematical parameter space with specialized pulls on particular collinear
quantities. As such, there is a clear complementarity among these programs,
with an opportunity for each to mutually reinforce and inform the others.
