If you want 1 general purpose gun that can do both, I'd say look no further than ICS. You can get a base gun and swap out upper cylinders for the 2 velocities.
If you want to take it one step farther, you can also buy multiple upper receivers / front sets. So say you want to run as a rifleman, you can have a full-length M16 front end and barrel paired with a 400 fps cylinder for long range accuracy. Then for indoors, you could have a 10" CQB front end with rails and a 350 fps cylinder.