In feel? No. The larger versions of their pens use the 21k nibs and the smaller ones use the 14k nibs, but there is no functional difference between them other than size.
On a side note, there is no functional reason to put more than 14k of gold in a pen nib; anything more than that is just for bragging rights and value as jewelry. A 14k nib is perfectly sufficient for resisting corrosion, and is actually better than higher carat counts for flexible nibs because it is less likely to be "sprung," or permanently deformed when pressing on it. Making a nib with a very high carat count is more difficult because a higher purity of gold is naturally softer, and needs to be strengthened somehow. So you could say that the 21k Sailor nibs are impressive for that, since they do have more gold than the typical 14k or 18k pens.
In my experience, the 14K nibs are better because they can be made flexible. Sailor has a lot of confusing models, the 1911 has a 21K nib, the 1911M has a 14K but is smaller...so now I'm wondering what to go for.