I am licensed in California as both a PG and a Civil PE, and can comment on the relative utility of both degrees. Note that California, unlike most states, has discipline-specific PE licensing, so I mean Civil PEs specifically (PEs in other disciplines have little or no authority to address environmental or geotechnical issues in California).
In California, PGs routinely conduct environmental and geotechnical assessments. In the vast majority of cases, Civil PEs are also allowed to conduct such assessments. Civil PEs can also prepare environmental designs (e.g. remediation systems) or geotechnical designs (e.g foundations), which PGs generally cannot do.
There are a few issues in California where a PG stamp might be required (or strongly preferred) over a Civil PE stamp. Some possible examples:
- Mapping the location, and determining the history of movement, of earthquake faults or landslides;
- Evaluating natural background concentrations of metals (at sites affected by metals contamination);
- Disposal of wastes by deep-well injection (typically down old oil production wells);
- Modeling the effects of proposed water-supply wells on aquifers;
- Evaluating naturally-occurring asbestos in serpentine bedrock (an issue in parts of California).
Of course, it's quite possible that these points don't apply in Florida (probably you aren't too concerned about active faults, for example). My guess is that if you are already a PE, then it's likely that the PG will give you little, if any, additional stamping authority. But the PG and PE together will look good on your resume.
I can't comment on the relative difficulty of current PG vs. PE exams. I've had 16 hours of geology licensing exams (the old 8-hour California state RG exam, plus the 4-hour California state certification exams in hydrogeology and engineering geology). Cumulatively, the geology exams that I've taken were comparable in difficulty to the NCEES FE/PE exams (not including California's supplemental seismic exam, which was more difficult than any of the others). However, most or all states (including California) now use the 4-hour ASBOG FG/PG exams for PGs, and these are supposed to be easier.