Of all the games trap requires the most muscle memory. Take a dedicated trap shooter quail hunting and some
of them can't hit squat. 3 gun shotgun is typically not all that difficult and is more about speed. If a person shoots 5 stand they develop their overall skills and it carries over better to HD, hunting or 3 gun. It is also an easy and affordable way to practice. The people you shoot with on average will be more laid back. Especially on open to public days or ranges.
Trap requires precision, focus and consistent technique and set range of possible angles. Being able to hit a hand sized disc going away from you at 60mph just does not do a lot in terms of practicing for 3 gun. It tends to appeal to the more anal retentive personalities. Hence the possible tension you may experience at a trap club. On the other hand guys like that won't shoot with people they don't know on their squad.
Sign me up!!!
But seriously, I don't shoot much, mainly skeet with friends, no leagues or groups. This sort of sounds like the OP. If that's the case, OP, get a gun for 3 gun, and consider something with a removable choke.
Remington 870
I guess you should get an 870 - INGO has spoken.