WYR take a $100,000/year contract for 4 years, or a $200,000/year contract for 2 years?
Imagine that you are considering two attractive job offers.
Company A will pay you the total of US $400,000 for 4 years of work, structured as a $20K signup bonus and the annual salary of $95K for 4 years. Company B will also pay the total of $400,000, but for just 2 years of work ($20K signup bonus and the annual salary of $190K for 2 years).
Other than the salary levels, the two jobs are nearly identical: both are in the same occupation for which you are more or less qualified (which is your current occupation, or one into which you would like to enter), in similar locations (either in your current city/region, or in some other city/region/country to which you'd like to move for those 2 or 4 years), and involve essentially the same work in very similar work environments, with the same number of hours or days worked per year. Both employers provide identical benefit packages, as appropriate for the industry and the location, as well as any necessary legal support (such as any occupational licensing if required, security clearance if needed, or a temporary foreign worker permit if working outside of your country of citizenship). You are subject to the same taxes as everybody else in your circumstances.
Regardless of whether you work at A or B, you will enjoy the same level of prestige and social status (if any) that your occupation entails in your community. Nobody (outside of the company's payroll office) knows your salary.
As to the job security, both companies pretty much guarantee your employment and wages for the duration of the employment agreement (4 or 2 years, respectively), as long as you perform your duties in a satisfactory manner. However, an extension beyond that point is very unlikely, as the job is for a limited-duration project. Of course, you can use your gained work experience to seek a job elsewhere after the end of the current employment agreement.
There is no penalty per se for leaving the employment early (other than the repayment of the signup bonus), but if you do so, you may find it difficult to find another job in the field, as the employers all know each other and don't like job-hoppers.
(If salaries or wages in your current occupation or desired occupation are higher than US$100K/year, let the two offers be $X*1.25/yr and $X*2.5/yr, respectively, where $X is the median salary in your occupation).
Which offer would you prefer? Higher pay (B) or longer-term security (A)?