Hi Astrid and welcome to the forum!
Admittedly, to me, smartphone pictures are totally irrelevant. Therefore I am not the one to advise on the qualitiy of the camera.
But there is a thread about comparing the pictures of the camera, you could be interested in reading:
Still, in general I would side with your boyfriend in this regard.
If pictures are important to you, opting for the new camera seems sensible. While both cameras are shooting 12 MP pictures, the ones with the new module are using quad-pixel technology, thus enhancing low light quality. (At least, that’s the advertising of Fairphone and the camera-chip manufacturer. I can’t judge by own experience.)
In addition the FP3+ has an updated audio chip and speaker module.
Therefore it lacks a translucent back-cover (due to a higher percentage of recycled materials) and a bumper.
Regarding bugs, you will find, when browsing the forum, that there are quite a few parallel bug reports regarding the FP3 as well as the FP3+. The reason is, that the most important bugs seem to be related to the update to Android 10.
As it seems, it depends in part on the country and networkd provider if you are affected by some bugs. But Fairphone is busy working on solving those issues.
Still, the majority of phones seems to work flawlessly. This forum is no exact mirror of reality, as it is usually visited when problems or questions occur and not just to tell, that everything is fine.
Maybe there will be some users here, that can give you more or bettetr advice on the camera.
In any case I still consider my FP3 (running on /e/) to be a great phone. But I have bought into this idea with the FP1 in the preorder phase already (my wife is using hers still as one and only phone). So I might be a bit prejudiced.