With the TF gun, Variant #1 of whatever is usually the default and it goes up to #5 for a total of five forms. With the watches, there's apparently a base in addition to five variants for a total of six forms! Deliberate advantage given to the watches, or an oversight I've just decided to roll with? YOU DECIDE!
Of course, the fact that I'm even asking probably makes it obvious. Let's just all pretend it's the former.