Yep! More arms would provide better information about the polarization of gravitational waves and the direction of the source. Of course, just adding more arms to a single detector would have limited success because you can only really expand a detector in one plane, so it's more useful to have more than 1 detector in multiple locations on the globe, because each detector's orientation (and therefore, each field of view) is different.
Having the VIRGO detector as well as the two LIGO detectors is what [allowed scientists](https://physicstoday.scitation.org/do/10.1063/PT.6.1.20170927a/full/
) to pinpoint the location of the binary neutron star merger event last August, because the nondetection in the VIRGO detector limited the search to VIRGO's well-defined blind spot.