1946 S Jefferson Nickel, Same Mint Mark Or Different?

Nope...they are definitely different. I don't know about scarcity on nickels, because I never cared about nickels, but I can tell you your coin #1 is a serif mintmark and your coin #2 is a sans-serif mintmark. These are both common on Lincoln cents, with about 55% of coins counted to date being the serif mintmark, and 40% being the sans-serif mintmark. On Lincolns a third mintmark was used, the ball-serif. It is rather scarce and makes up the difference with about 5% of the coins found bearing this mintmark style. It is distinguishable in that it has a rounded ball shape on the top and a triangular lower serif.

Look on varietyvista.com. Go to mintmark styles then San Francisco then look under the nickel column. There are 2 varieties listed for 1946 nickels. One is called a trumpet tail and one is a sans serif. Neither is listed as being rare or scarce. By the way, good eye.