Sunlight - is radiant heat and should not be allowed to interfere with any temperature measuring devices.
Whatever sort of heat it is, doesn't it affect the temperature of the room? Of course, rule number one is not to put any thermostat where the sun shines. The extra delay due to the slow sensor in a TRV cannot be an advantage. The heating / cooling time of the room is there, whatever so no worries about 'smoothing out' any change in temperature. A room stat can be moved to a 'good' place in the room but a TRV is stuck where it is.
I should have realised this but, as you guys do not monitor the performance of your installations when you commission them, you can hardly be expected to be able to compare their performances from experience. Therefore, I can't expect an informed opinion about how well an improved (electronic) system can work.
If a customer asked you about installing a smart system, would you just tell them that TRVs are the only way to go? My life, just think of the profit already.