This is my thoughts on the whole secondary, not just the safties.
Our secondary is like a lump of clay, it's versatile and flexible, and can be anything. In fact it is this quality that will allow us to dominate teams. We have Jason Allen who can play CB and S, that means teams will have to keep an eye on him all the time. He can be lined up anywhere, and it will give defenses fits.
At S we have Allen, Hill, Tillman and Bell. Bell proved last year that he is capable of stepping up and playing. Any four of these guys can be plugged into that posistion and be able to contribute with their own special skills. This ability to not miss a step with different guys, will mean teams will never know who they're facing next.
At CB we have Daniels who was a solid starter in his rookie year, and will only get better. Renaldo HIll is another versatile guy that can play either S or CB, and will help create difficult match-ups for opposing offenses. I don't know much about Will Allen, but I gather from most of you that he can play. Lastly we have Will Poole. He showed flashes of brilliance his rookie year, and could have possibly been a starter last year if he hadn't gotten hurt. If he plays NB this year, it'll mean we'll have a starter quality CB as our backup, nothing wrong with that. But also Poole will be able to play CB 1 or 2 in certain situations, adding for increased versatility. While Poole may be a NB this year, I expect him to make a strong push for the starter position and be the starter next year.