I have heard both ways and was just wondering if I could get a clarification from everyones experience.  The main thing I have heard from a   friend is that a standard 223/5.56 will hold 25 6.8SPC.

No.

I think you can get four rounds in a 5.56 mag.
never tried shooting it that way though.

25 rounds? No. No where close.

I can load 6 or 7, can't remember which right now, in a USGI 20 round mag. They load easily and shoot just fine. This is what I use when sighting in from a bench. I can load only about 2 more rounds into a USGI 30 round magazine. There is simply no way to load more than these amounts. But either size USGI mag, in good condition, will shoot the 6.8 just fine, just at a very much reduced capacity.

6.8 mags are made of stainless steel. It has the rigidity that aluminum lacks. Aluminum mags bulge when loaded with 6.8 rounds. The grooves molded into the sides of the mag are different too. The feed lips are spaced and shaped differently.

Other than that they are the same.