5,5gb 'other storage'

Hi, I have GDR2 Samsung ativ-s with 5,5gb other storage - with 16gb total this is kinda bad. Now I'm willing to change my csc so GDR3 will be available, but I want to ask you (since I'll need to reset my phone anyway) should I do interop unlock - waht are benefits of that and what's best and easy way to do it?

Thanks in advance