Almost all the photos I see of the HST show the two small dish antennas at the ends of the two long, opposing booms with the "top" one pointed straight ahead at 12-o'clock, and the "bottom" one at 3-o'clock.
The HST is in LEO, and probably spends most of its time at an attitude either fixed (or nearly fixed) with respect to the stars so it can do science, or efficiently slewing to the next target. That means that these two antenna booms will spend most of their time without a fixed orientation with respect to ground stations on the Earth, or communications linking satellites in GEO.
Do these dishes actually articulate and independently track targets so they can downlink this constant stream of data and uplink their next instructions? If not, does the telescope stop making measurements, stop tracking the heavens, and slew around to point one or the other at communications links?
Either way (stopping science or extra work for ADCS turning the entire telescope) sounds less optimal than just adding articulation to the little dishes.
above: "An STS-125 crew member aboard the Space Shuttle Atlantis captured this still image of the Hubble Space Telescope as the two spacecraft continue their relative separation on May 19, after having been linked together for the better part of a week." Cropped, from here.
above: "The Hubble Space Telescope as seen from the departing Space Shuttle Atlantis, flying STS-125, HST Servicing Mission 4." Cropped, from here.
above: "The Hubble Space Telescope (HST) begins its separation from Space Shuttle Discovery following its release on mission STS-82." Cropped and lightened to better show upper antenna. From here
above: "IMAX Cargo Bay Camera view of the Hubble Space Telescope at the moment of release, mission STS-31." Cropped, from here.