San Diego's conservatism is one of its biggest drawbacks.
But generally speaking, San Diego is not hotter than LA, as more of it is in proximity to the temperate coast. And it's wayyyyyyy prettier than LA; they're not even in the same category. LA is a few hills with giant basins, San Diego is rolling hills throughout and very pretty. And due to those hills, San Diego doesn't have the "encased in concrete" feel of Los Angeles, which is both more aesthetically pleasing and doesn't try to cook you just because you're walking outside.
The Gaslamp is a great area and San Diego's beaches are more accessible and better.
And it doesn't require three days of driving in traffic to escape San Diego when you just want to drive somewhere for the weekend.