As both fields deal with rocks, soils, and other related topics both are very different fields with very different scopes and applications.
Geophysics, as you probably know, studies physics as it applies to geology, seismology, volcanology, etc. Geophysicists may work in a lab monitoring a seismograph, or they may be out in the field studying the flow of magma from a volcano. Some geophysicists work in the Petroleum industry or the Mining industry finding oil or mineral/ ore deposits.
Engineering Geology and Geotech Engineering are related fields with some overlap, but are still separate fields. Engineering Geologists investigate erosion, flooding, seismic activity, and other geohazards at a site to determine what may be needed to solve these problems. Geotechnical Engineering is actually a subfield of civil engineering dealing mostly with foundation engineering, soil mechanics, and rock mechanics. Geotechnical Engineers are mostly needed at construction sites determining how to pack soil and prepare foundations for buildings, dams, bridges, etc. They also may figure out how to make a building earthquake safe.
Both fields use physics and geology, just how it's applied is a great difference. If you want a good high paying job in the Petroleum or Mining industry, go Geophysics. If you like construction sites or designing a system for controlling geological hazards go Geotech. As civil engineering and construction are supposed to be growing, and the search for new oil and mineral deposits continue, job outlook for both fields are supposed to be pretty good.
