simple RECOVERY mode, but with not static data About recovery modes, I know that if you want point in time recovery, we should use FULL recovery mode. if this is not necessary, you can use SIMPLE recovery mode.

But, I read about Simple recovery mode, and it says that we should use this if point in time recovery is not important and if your data is static.

Here we don't need LOG backups, we only use Full backups and Diffs, and I thought that should be good for performance and disk space to use Simple recovery databases. But As I said, we don't have static data. there's a lot of insert, updates and development updates ( yes I don't understand why they don't need point in time recovery , but, anyway...).

My question is, is still a good Idea to use simple recovery, or by not having static data, the log will still grow, and etc?
Ultimately, your recovery model is dictated by your business needs.

It all boils down to the question "How much data is it okay to lose if the server goes belly-up?".  

With FULL RECOVERY, that time is dictated by the time between log backups (and can be reduced if a tail-log backup is available).  You manage the log backups and how full they get by taking LOG backups.  If you don't take log backups, the log will simply continue to fill until it runs out of disk space.  At that time, transactions will fail due to insufficient disk space.

With SIMPLE RECOVERY, that time is increased to the time between the current time and your last differential or full backup.  The log is managed by CHECKPOINT operations that occur automatically behind the scenes (Recovery Interval).  Unless you are doing transactions whose size exceeds the size of the current log file, it won't grow.

This is also under the assumption that your backups do, in fact, work.  Backups are only valid if they can be restored successfully.

I'd recommend putting these decisions in the hands of your superiors after you present to them what the differences are and what that means in terms of RPO/RTO.