Just remember how employers have NO loyalty to "you" the worker. Id say they take whatever job is the best and highest paying. Its too bad if their situation changes and they want job C. They owe NOTHING to any of these employers. As the employers wouldn't hesitate a second to cut you loose. And also follow the other advise that you NEVER tell any employer that you are looking for another job or taking interviews or that you have been made an offer. The employer never gives the worker the heads up that they are looking to replace you.
This.
As a highly credentialed seasoned professional who was 'acquired' in an acquisition of my wonderful little company by mammoth IBM 2.5 years ago, I have been sitting around for those entire 2.5 years watching the top guys at IBM lay off tens of thousands of highly skilled professional workers (accountants, engineers, software developers, skilled project managers, techies of all kinds) in the US and Canada, despite continued IBM profits in even the worst of times...and replacing those loyal people (many of whom had been with IBM 25+ years and were gypped out of their pensions in the layoffs) with cheap and incompetent labor in Brazil and India....who now rely upon the few Americans and Canadians left to do their jobs for them because they are so utterly incompetent and lacking in any sort of urgency about deadlines, work quality, or anything.
For these 25+ year IBM employees laid off, IBM had barely a word of thanks to say. It was very much a case of "Don't let the door hit you in the ass on the way out!" And this is toward hard working, competent people who had poured their entire lives into that company.
The moral of the story: The Man does not give one solitary SHIT about you. And would replace you in half a heartbeat with someone with a quarter of your skills, if they offered to work for half as much.
Greed on the part of the top guys in these companies is ruining said companies - because these guys are more concerned with short term profits (which effect their massive bonus checks) than they are with the long-term health and reputation of their own company (which they will likely not be around to see, given the short shelf-life of your average CEO). When you reach the point where 'doing it cheap' has become more of a priority than is 'doing it well', count on the fact that management no longer values it's most valuable resource - competent, professional, highly skilled workers.
Tell your friend to do what is right for THEM. Because I assure you, The Man will always do what is best for HIM. Even if it means screwing over those who have been the most loyal and most hardworking employees.