What is exactly "slow"?
It's takes a time to given query output . Same query provide faster output in a toad.
Are execution plans different?
I can't check it . Is execution plan are vary on development tools ?
It could change, yes.
If memory serves me well, in Toad you have the possibility to indicate default hints added to each query. The "FIRST_ROWS" hint is often used as default there I believe.
I suggest you to check the toad's parameters, and if the hints are used there, try to add the same hint to your sql statement in sql developer to see if the execution plans become the same.
And make sure you're able to get the execution plans in both applications, this is indispensable for any professional developing sql. Without the execution plan you're driving blind.