[Captain Ahab Jr]

I would go back but ask if the salary is negotiable, if not when you start can you agree (in writing) a schedule for annual increases as you're experience grows.

If you look from your old companies perspective, they know you, they know you will fit in, they are also pretty sure you can do the job. You have a huge head start on getting the job compared to any unknown applicants so if they have any sense I'm sure they will find a little extra to reach a mutually acceptable salary.

As for security, the best job security you can have (other than a long term contract) is knowing you have the right skills other companies are looking for.

As mentioned before you spend most of your life working so if given the chance you should choose which one you will enjoy the most.