I have not noticed any difference between: paid F, op up, electronic upgrade, miles based upgrade, exp complimentary upgrade, SWU.

Have occasionally had EXP status mentioned by FA during the welcome. One did welcome people differently based on status (e.g. "As EXP you are one of our most important customers" vs "As a Platinum you fly a lot with us and we thank you"). She got a thank you coupon because she was very attentive and remembered my name during the flight (oh, the little things).

The FAs occasionally treat you differently based on whether they personally recognize you (e.g. one remembered the tv shows I was watching on the flight from DFW to MEM and then commented on them on the return flight a couple of days later).