Suggest look carefully at the in-college and major requirements for development sociology.
I’m sure there is lots off room to take credits in other areas, but you should still get a good handle on exactly what you will have to take if you enroll there.
Transfer to AEM or CAS is not uncommon, but your ability to do so cannot be absolutely guaranteed. Especially I just read on CC that AEM freshman admit rate was 3% !!. So you should not base your whole decision on the assumption that you will transfer to another college/major. Though that may prove to be the case.
IMO Cornell probably has more economic diversity than most private colleges, since its reduced tuition for in-state students attending the contract colleges is very attractive to the non-rich.
As for the weather, I’ve come to accept, by reading CC, that a certain proportion of people coming from warm-weather states are petrified of the thought. It is what it is. You can be petrified, or you can decide there ae bigger issues and deal with it. IIRC, some of Cornell’s biggest contingents of undergrad students come from California and from Texas.
If you prefer the curriculum and program of studies you would get if you enrolled as a development sociology major at Cornell, I would recommend that you deal with the weather and go there.
If you prefer a liberal arts curriculum, and you prefer UCLA in all other respects, go there. But look at the course/college/distribution requirements for those programs too.