I think it depends on how you see your future. If you see yourself as an IFR Twin pilot in the GOM then I would go the SIC route and build time with experienced IFR Captains in an IFR style environment. This way, you will be able to learn the best from everyone you fly with. Your operating style will become disciplined and you will be exposed to the full spectrum of simulator and CRM as well as medium and heavy time with some good type experience which could be useful for the future. (Bell 412 or S76)
If you see the future as a contract or utility / fire type pilot then do the next 400 hours instructing and see what happens from there.
My only advice would be that if you have worked for a stable company like Bristow, PHI or ERA for a couple of years in whatever capacity, you may find it easier to get employment in other places. If you have only worked for small companies and done short term jobs, the larger companies will question whether or not you will stay with them and their investment decisions in you will be examined closely. If you can get an SIC offer in the GOM, I would take it and look at your options once you have a couple of years experience.