I have used a Jandy 3-way to fully open all three ports at the same time so it basically looks like a tee. The opening for each port is about the size of the pipe so restriction should be low.

The valve can be set up to rotate the off position through the middle port or away from the middle port. The later allows you to rotate the off position to where there is no port (opposite the middle port) thus allowing for all three ports to be open at the same time.