You sound like you'll be happy in any version that runs well. There isn't a huge difference in weight. The options were adopted over time. My 280 is identical to a 250 with the exception of displacement. It is not true that all 280s have headrests, although they are a valuable whiplash preventive. Not all 280s had shoulder belts, but you'd be foolish to drive daily without them. The power steering is a big help in a crowded downtown.
I don't know what year you used to have. Obviously, the greatest differences are between a '63 and a '71. From what I have read here and from owners I have spoken with, the '70 and '71s with automatic and air conditioning have the greatest challenge in hot weather. I think this is due to the ignition timing and emission control. My '68 manual with air doesn't run hot except when stopped a long time in traffic over 95 degrees. (Does that ever happen in LA?
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I would guess you want a/c in SoCal. Perhaps some of the 230 owners can tell you how well the smaller engine handles the heat with air on.
I chose the '68 because I believe the "68 and '69 are the peak execution of the design. Best brakes and best engine unchoked by poor emission regulation.
That said, the nuances of the differences should not be your prime concern. A good, safe, rust-free car is your prime concern. You'll be admired for driving. and keeping alive, any of the three models.
Good luck, and post a photo when you buy your new auto companion.
Ray
'68 280SL 4-spd Coupe