Resigning vs Being Fired
Resignations, and being fired mean very different things on your resume, and in some cases to your career. Being fired is based on the employer's prerogatives, but resigning is your option. It's important to understand the ramifications of both.
The Results of Being Fired
If you get fired, you do not have control of the situation. The employer pulls the plug, regardless of your needs or circumstances, and you're stuck with the results. Being fired is a scar on your resume. Even if you aren't at fault, being fired is a career liability. It can create career detours and severely upset domestic situations. The job hunting obstacle course that created is not fun. People eventually overcome being fired, but the time and trouble experienced in the process is a setback.
Explaining why you were fired is difficult in an interview. You also have to exercise a lot of tact and restraint to avoid expressing your feelings on the subject and the former employer. Employers react instinctively to people who've been fired. They do need to know the circumstances, and it's difficult to put questions about it tactfully.
The Results of Resignation
If you resign, you can control when, where and how that happens. You can plan ahead. Even by implication, the circumstances of a resignation are quite different to being fired. There may be some difficulties with resignations in terms of employment law, like in the US, where if you quit, you're usually not eligible for unemployment. That's not always an issue, though, and many people resign for good reason.
The people who resign are usually better set up to deal with the situation than those who are fired. The most effective resignations are planned in advance, with all the loose ends experienced by people who are fired under control. In the employment market, resignations are viewed quite differently to firings. If someone walks out on a job, logically, there has to be a reason. The person who resigns is somewhat more credible in job interviews, because the reasons for leaving can be very convincing. If someone says "The job was going nowhere, and I didn't see a future.", it's much more plausible. It doesn't sound like an excuse or self justification.
Some of the reasons for resignation can be impressive, as well as honest, in job interviews. An applicant who states that they left a job because it conflicted with their professional ethics is making a significant statement. Particularly if they are applying for an accounting position, where ethics are a real issue.
Resignation vs. Being Fired
In terms of having control of your working life, resignation is preferable. You can call the shots. Being fired means having to move into damage control until you can put the issue behind you. A resignation must be carefully considered and well organized, but it's a safer option in many ways.