Sell Fuji XT3 or XH1 to buy XT5?

In reading your original post, it sounds like the XT3 is your primary camera, and the XH1 is mostly gathering dust. They are both excellent cameras that are capable of producing excellent image quality. The XT5 is a wonderful camera with several improvements over both; ibis, 40mpx, latest processor, improved AF, etc, etc..and whatever bugs there might be in AF will certainly be addressed in firmware, but still the AF will not be as good as Sony, Canon, Nikon Z9, or the XH2s. To me, you need to answer the following questions for yourself:

1. Why do you want to upgrade, latest toy or is there a specific feature(s) that you want or need?

2. Why do you need or want two camera bodies?

3. do you shoot professionally or is this a hobby?

4. if you prefer the grip/body of the XH1, why are you not shooting with it more?

5. Have you considered the XH2 or XH2s as options? One point worth noting is that XT3, XH1 and XT5 have similar LCD screens (3 way tilting), while the XH2(s) have fully articulating screens…I would have purchased the XH2, but wanted the tilting lcd and purchases the XT5

6. Are you working against a certain budget?

There are no right or wrong answers here as these are personal to your situation, but is maybe helpful in your decision making process. You cannot go wrong here, but there are trade-offs.

If it were me, I would sell the one that has the most value in the used market (XT3?), and purchase the XT5., Maybe sell both? Or milk the bodies that you have and buy some lenses.

Good luck.

Rod