SASless, if you won't buy "workload" as a reason to operate S/E in the GOM, how about (Gasp!) safety? I've lost the link, but there was a study done a couple years ago in, I think the UK, that showed that single-pilot twins had a poorer safety record than singles? The GOM has many factors that make it dissimilar to the UK and the North Sea, but they all should act in favor of the present mode- S/E.
There's an an accepted, analgous heresy on the fixed wing side of aviation- again, "light" single-pilot twins have a poor safety record. The commonalities in the two, fixed and rotary single-pilot twins, and accident rates is this, in my opinion: They're not very user-friendly.
Logically, there really should be a safety advantage to even limited power redundancy- that's common sense. That wished for safety advantage is especially tempting when one's working in region of increased risk- limited forced landing areas, for example.
This results in the real world pilot being: in an aircraft that's designed using big-iron ergonomic principles, e.g. overhead throttles; operating it in a more hazardous situation; in an aircraft that's more likely to have issues because of systems complexity; and the crowning touch in the safety hallucination- the pilot thinks the aircraft is SAFER!
Evidence? Look here:
http://www.ogp.org.uk/pubs/366.pdf
A quick glance thru yields:
Accidents per 100k hours- Single engine (turbine) 4.73, light twins 5.26.
Per 100k stages flown- S/E (T) 1.31, light twins 2.1.
Pretty much as I recall the '99(?) report.
I flew the GOM SE and twin, and they *fly* the same. The workload in a twin is higher- systems management.