Well, it depends on what you want...
Lure is so common, and it gets boring after a while that EVERYBODY has the same gag as you. It is, however, quite easy to use, and quite easy to maxx after you get it into higher levels (Pretty much like any gag).
Trap is un-common, and it's a fun gag (to from what others have told me, I personally don't have trap) to have. And although the unusal-ness is refreshing for a time, it comes at a price. Trap is hard to train, unless once again you get into higher levels. Another thing is, you need Lure to use it, and since you already don't have it Lure, you always have to be fighting with a buddy if you wish to use it. One more thing is that you can carry less gags than usual.
Summerized down:
Lure: It gets boring after a while because it is so commonly chosen, but at least it's an upside for soloing, and you can help others with trap. In other words, think of this as the blue pill.
Trap: Choose this if you wish for a challenge ahead of you (So what others have told me). Trap is the strongest gag, and it's really good for bring down cogs. It never misses if lured in, and it is also uncommon, so it makes you the few 1 out of 10 that has it (Just an estimate

). Bad sides are that you need someone else to lure cogs into the trap, unless you have it yourself (Which in this case, you don't). Another thing is, you can carry less than usual of it. Think of this as the red pill.
This is just soley my opinion, and the choice is entirely up to you, so don't feel pressured by others telling you what to pick. I hope, however, that this gave you a godd idea of what might be ahead of you.
Hope this very looong summary helps!
mickysinasock
P.S. If you already have Drop, perhaps you shouldn't bother with Trap, because you already have a strong gag. It is, although, still up to you.