Stacking Port Usage on 3448

I have a pair of 3448's in the rack along with a 6248. I am using the 6248 as my core L3 switch.

I have had the 3448's going back to the 6248 using port 47 as a trunk. Since the ports are all 10/100, I am pondering the benefits if I could use one of the Gigabit Stacking Ports instead of a standard 10/100 to go back to my core switch.

So I have 2 questions that I am hoping that someone might be able to answer;

1.) Since I am not stacking currently, can I use G3/G4 as a standard trunk rather than a stacking port?

2.) Would there be much bandwidth difference to the users on the switch by going to the Gigabit as opposed to the standard 10/100 that is tying the switch back to the core?

Any help would be appercaited. Thanks!