The only "pro" I can think of, is using the extra water to give you more flexibility in managing the pond.

However, to utilize the extra water you probably need to increase the freeboard on your dam significantly above the normal pool level.

You could hold an extra 3' of depth after a heavy rain in July to get through a brutal August. You could flood the grass around the pond during the spawning season for your baitfish. After the fry mature, draw it down to feed the gamefish.

I doubt the benefits would exceed the expense, unless you had lots of extra dirt to spoil. In which case, building up the dam might be the best place to put it.