"I like this apartment building, but I prefer the red one."
Translation:J'aime bien cet immeuble, mais je préfère le rouge.
I'm guessing the use of it here kind of comes from how it's used for people. To say that you "aime bien" is to say that you don't quite "aime." So saying that you feel that way about an object would make sense if you were comparing it to something that you liked more. That idea makes sense to me anyway, would love if sitesurf had any input on that
thanks for both of those clarifications, which gives us two premises: 1) we can use 'aimer bien' or 'aimer', and 2) as the context of the question was apartment building, the answer should specifically mention the apartments, should it not? so as not to be confused with any other sort of building, for example the office building that may be next door to the apartment building; and especially noting that DL can rather pedantic; I have cut and pasted below my exact answer below, which was marked wrong, and I would be interested to now what is actually specifically wrong with it:
"j'aime cet immeuble d'appartements, mais je préfère le rouge"
"Un immeuble" by itself and by default is an apartment building. The alternative is "un immeuble de bureaux", which specifies that it is not an apartment building.
If you want to compare an apartment building and an office building, you will use "un immeuble d'habitation".