I can be from cold to 425-450 within 20 mins or so. I have a hunch that the Memphis will be faster for reverse sears. It takes probably 10 mins to go from 250-450. I think the Memphis may be 1/2 that.
Are you referring to the Pro? I think the Elite takes at least 10 minutes to go from 250-450 - OK now I'll have to measure
But I don't do reverse sear on the Elite because it does take too long. And to get a good sear, you need to hold at that temp for at least another 5 minutes to get the grates to catch up.
These days I smoke on the Memphis and then sear on cast iron or over charcoal. For just straight searing, the Memphis works great.