I'm just wondering if it would be a good comparable when referring to operators and oilfield services companies. To be specific for reservoir engineer or any subsurface positions.

From my understanding, reservoir engineer tends to be station in office and working on simulation, dynamic model, analysis and etc etc using sophisticated software programs.
While those are 4 big contractors theirs business are mainly to provide services to operators like Petronas, Shell, Exxon and so on. So these kinds of jobs are done by field engineer or field specialist which come from different segments (wireline, completion, cementing and etc). So the opportunity to get your hands dirty, working on site with big money is there.

Yes, I also know that these 4 big contractors have their own subsurface team (G&G, Petrophyscist, RE). I think these people also more likely to work in office based. Very rare going to the site. (Correct me if I'm wrong). Their working nature more or less same with operators which emphasize on consultancy services.
IMO, field people (FE or FS) cannot be compared with those working in subsurface team doing all FDP stuffs at office. Money wise, as I know both of them get very good pays.

I'm going to graduate soon with MSc Petroleum Engineering, but feel uncertain with job prospect in Malaysia