You speak about “Counter offer by current employer” but I would like to know what do you feel about this offer? Is this better offer than the new employer has offered you? And, do you feel you can get more good opportunities and growth with new employer than the present or what you expecting from new employer in comparison to your present employer?
See you have spent a good time here I presume and are well familiar with the work conditions and everything with present employer; therefore, you are the one who can judge these conditions first and have to decide which better one for you is. Please let us know what you feel about it too.
Second, do not forget to consider the reasons that put you in this condition. Reasons, which forced you to resign from the present position/employer, and it is also important to realize that this “Counter Offer” evidently says how important are you for your present employer and they appreciate your skills and work performance which is why they wanna retain you.
Apart from that in simple words, I would suggest you to accept this counter offer and continue with your present employer, and for this why you should continue with your present employer, I also would like to present some other facts that will help you to understand the same for sure.
-You are well familiar with the present work conditions and other with your present employer that enable you to work with a good understanding but with new employer to get the same you certainly gonna take time (if joins) which is why you should continue with present employer.
-You have resigned but still your Employer likes to retain you that says about your work performance and trust they have onto you, which I believe is m important for an employee and give you more chance to get your position strong there and further promotions.
-Counter Offer automatically says a good hike in salary and other benefits and as more growth options, work responsibilities, more learning, and a value that employee holds for an Employer and the same expect from new employer so easily or early. Every employee wants to be an essential part of an Organization, expect a value with respect, and strong & good position that matters too, and with present Employer, you are getting the same.
-You can get many new and more good offers in future with many reputed employer/firms but the value, trust you have gain is not so easy to earn which is why I feels you must continue with your present employer. Also in this outer world, opportunities always dig the footsteps of the right, skilled and experienced candidates, so you can get the same in future whenever you feels to go out.
Now I would like to ref the statement/suggestion provided by Ms (Cite Contribution) that you must be honest with yourself and your new employer. Please tell them that you are not going to join them (if decides to continue with present employer) which will also be a good example of professionalism.
Lastly I would suggest you to consider the reasons of your resignation before taking any decision and im sure the same gonna give you lot more to learn for your future and career.