Sell the asset or take more credit?

Even though prices for building land tend to rise, I would personally sell. You have no use for it, someone else can make something out of it, and you have more equity to build your house. Ideally, without any loan. Life is definitely more relaxed that way. You also don't have to worry about it anymore. Later, you will inherit a house. What you do with it then, you have to decide based on the situation.

if you have no use for it then sell. Everything else is speculation and now you can use the money well. please also consider possible fees when selling

Why Either Or?

How about selling the distant property and keeping the nearby ones? That way, in my opinion, you would have a healthy mix and you can also offer some building land to your descendants.

Only resulting from gut feeling. One keeps property if one does not have to sell.

I completely agree with Osnabruecker.

I would sell the more distant one to reduce the loan amount and improve the terms.
I would personally keep the other one.
Most of our acquaintances who can still afford to build a house build on a plot of their parents. I would never completely give up such an option ;-)

How about selling so much that you can put up an apartment building for rent on the remaining plot with the proceeds? But you have to like being a landlord.