The 350c is vastly superior to the PS Engineering.
The Telligence feature alone knocked the 450 out of consideration for my panel upgrade.
Other than Telligence, what features of the Garmin audio panel make it "vastly superior" to the PS Engineering one?
In my case, I chose the PS Engineering PMA 450B for the panel upgrade in the 310. Here are the reasons why:
1. Compared with GMA 35c, no loss of always-there data fields on the GTN 750. (I lose 2 fields to remote transponder control even though I have a GTX 345 with its own control panel. I use the other 4 for TRK, DTK, DIS/BRG APT, and Tuned VOR info and then on my map page I have shortcut keys for checklists, approaches, and nearest airports along with the VSR field in one corner.)
2. Compared with the GMA 35c, front-panel access to isolation modes. I've posted about this several times, but for me it is important to be able to switch between Pilot, Crew, and All during busy phases of flight. For example, during an approach, I like to be on Pilot to let the passengers deal with each other, but switch to All to check on seat belts and such, and then switch back to Pilot. I use Crew similarly when I have a helpful person in the copilot seat, to check on the passengers for me while I focus on flying and radios. The GMA 35c requires you to go to the Intercom page and then navigate the various intercom pathways repeatedly, on a device you need to use for other things. (In my case, it's my checklist, flight plan, and moving map and I have the approach plate up on the nearby split PFD/MFD.)
3. Compared with the GMA 350c, better front-panel access to isolation modes. One button that toggles from Pilot-All-Crew-All-Pilot and back around, one step each time it's pushed. The GMA 350c has Pilot, Copilot, and Passenger buttons. I think it is easier, in the heat of battle, to navigate the isolation modes of the PMA 450B than those of the GMA 350c. (Edit to add: I just looked at the GMA 350c manual. The isolation modes are described on pages 17 through 22. The PMA 450B manual describes isolation modes on pages 9 and 10.)
4. Dual bluetooth channels. It's nice to be able to listen to an audiobook while the passengers listen to music or watch a movie. This is a secondary item for me, because I'm not a YouTuber (one of the channels can be used to record the intercom/radio audio instead of streaming into the panel) and I could use a bluetooth headset to listen to something at the pilot station while everyone else listens to a shared bluetooth source over the intercom.
I enjoy the audio panel in actual use. I've never longed for anything different. But I'm always quick to recognize others' preferences vary from mine and eager to understand why.