Before you quit your job to work for a competitor, you may want to consider the following:
Review your agreement. Does it contain a non-compete clause? If yes, you may be required to stay and work with your current employer for a period of time before leaving to work for a competitor.
Is your new employer requiring a letter from your current employer? If yes, be prepared for anything. Your current employer may write a good or bad review, and you may not have a chance to appeal. This may affect your potential future employers.
How is the relationship between your current employer and your coworkers? You may not be able to please everyone, but you also do not want to upset or strain relationships with coworkers. Sometimes more money is not the answer to everything, but great relationships with coworkers and managers can make a huge difference in terms of job satisfaction.
Consider other opportunities and benefits available to you from your current employer versus the new employer and make decisions based on your own situation.
What is the nature of your current or future company? Is it a startup with growth potential that you need to grow with, or is it an established company with a great track record?
What can you do to change the situation with your current employer? Is the situation better with your future employer? If your current and future employers are in the same industry, is this other company going to stay in business? Examine their books and ask questions, for example, why they need you, why did the last person in this position quit, are there any recent layoffs, and what guarantees do you have that you are going to keep your job?
Check your emotions. Are you overreacting? Can you adapt?
These are just a few tips to add to your list before you decide whether to stay or go.