"That’s what does it for me"

word by word translates to:

C’est ça qui le fait pour moi.

This resemble the French casual expression:

Ça le fait → It is properly/well done, it is the right way

but it is not exactly what the English one means.

Your translation is quite good, and likely the one I would have suggested too:

C’est ça qui me plaît.

All three alternatives you found have issues:

Ça me branche → "I’m interested about doing something (in the future)."

Ça me botte → "I like it a lot" but very outdated.

Ça m’interpelle → Frowned upon, "I’m concerned about it; I feel the need to react."

Other suggestions can be:

• C’est (ça) mon trip. colloquial but doesn’t work when followed by "chez toi".

• C’est (ça) mon truc. common, same issue with chez toi.

• C’est ça que je kiffe. This is banlieues slang going mainstream but it isn’t usable by everyone and far too colloquial.

Note that your introduction is too formal French to be followed by anything colloquial. To stay in the tone, that would be:

Vous veillez sur nous en permanence. Il n’y a que quelqu’un de vraiment gentil pour en faire autant. C’est ce que j’apprécie particulièrement chez vous.

Your translation of the meaning:

C’est ça qui me plaît en vous.

is actually more appropriate than the other suggestions you make. You could, however, change it a bit like this:

C’est ce qui me plaît en vous.

Using “ça” puts a lot of emphasis on the object (the fact he/she is watching over you): it’s like saying “It is that thing, that I like about you”. On the other hand, using “ce” puts more emphasis on the “vous” at the end of the sentence: it is like saying “This is what makes me like you”. Using “ce” also feels a bit more natural.

You could shorten without ambiguity it by using just:

C’est ce qui me plaît.

This gives much more importance to the “plaît” word, and produces more impact, overall.

Regarding your suggestions, I fully agree with jlliagre. The first two are quite outdated, and none of them would fit well.

Contemporary and idiomatic? Just the simple word “cool“. But, like some of the suggestions above that wouldn’t mesh with the OP’s example too well:

Vous veillez sur nous en permanence. Il n’y a que quelqu’un de vraiment gentil pour en faire autant. C’est ca que je kiffe.

No, you couldn’t say that IMHO, the language register/level is not the same.