There were key differences.
On the left, the guard of the hilt goes all the way up and curls back at the top. On the right, the guard pierces through the handle at 2/3 of the hilts length and comes out at the other site. Also the pommel of both swords is different. On the left, it looks like a bell wrapping around the handle. On the right, it's a straight pommel. The design of the handle itself is also different. On the left, the handle is braided like a Katana. On the right not. Also on the left, the guard and the pommel are one piece, while on the right, the guard doesn't fuse with the pommel.
In chapter 1, Shanks had a sword resembling the left one. Later in Marineford he had the right one (Gryphon) and post TS Oda just changed it back to the old design.
It's obvious these are two different swords. It's not just Oda changing the design back and forth on a whim.