If he upgrades the client only, he will get the new features.
He will just miss the default aircrafts using these new features (the F-16 is the only one, though...).
I would recommend updating only the client and the content.
Also, be aware the 4.4 content does NOT include the Beechraft airplanes anymore, which means the Baron, the Kingair and the Carenado A36 will be gone. Not a great loss for the first two, but you might want to make a backup copy of the A36

(and its gauges too)
Also, you might want to check if any of your freeware aircrafts are using the default Baron or KingAir sounds by alias, or stuff like that.
Prepar3D Content
New Content
AC11 Commander 114 user-selectable vehicle provided by Carenado.
Indago UAS is now a user-selectable custom vehicle with auto-land capabilities, tracking camera, and custom UAV control scheme.
Several large explosion effects.
Generic torpedo weapon.
Reintroduction of VEH_air_firetruck that was removed in a previous release.
Generic 60ft Pusher Drone AI object with PBR textures.
Drone 3 AI object with PBR textures.
MHTK Launcher box AI object with PBR textures.
S-97 AI object.
81mm mortar weapon and launcher with PBR textures.
Fixes and Improvements
F-16 aircraft fully updated to PBR for both the interior and exterior models.
Added example targeting pod to F-16 cockpits with controllable camera, IR sensor modes, zoom control, ground and entity targeting, and weapon target syncing.
Tail numbers can now be modified on F-16s, C-130s, MH-60s, UH-60s, and CH-53s.
Added laser weapons as an example to LCS variants.
Added friendly names to F-16 controls.
Added dynamic lighting to the F-16 afterburner.
Added the new torpedo weapon to the Ohio Class Submarine AI object.
Fixed texture errors on C-130 fuel tanks.
Fixed flag textures on C-130s.
Added RecordAndPlayback.xml file and necessary set/get functions for Driver ISimObjects. Updated/removed unused control mappings.
Fixed ghosting tail number for 3 different F-16C variants.
Slightly repositioned eyepoint in C-130.
Updated MH-60s and UH-60s with animated Turn and Slip ball indicators.
Updated the AC-130H gun effect so that it no longer lags behind the aircraft.
Updated AC-130H gun effects and moved attach points.
Fixed issue preventing Howitzer from firing in the correct direction
Corrected several Desert Hawk 3 animations and materials.
Additional tuning and stability updates for Desert Hawk 3 including improved waypoint following.
Added pilot camera to Desert Hawk 3.
Removed ground bump from Orion and SLS.
Fixed typo in C-130 payload.
Updated S-97 AI object animations and tuned contact points, lights, weapons, and various other properties.
Added missing DesignSpecs section to various animals.
Fixed crash seen by some users when opening the ACM panel in the P-38.
Updated mouse pad textures in control towers.
Removed all Beechcraft (Textron) related aircraft and scenarios.