Zwiftpower.com question

I see zwiftpower has me at 20 watts ftp lower than what I have my ftp set at. Should I go with zwiftpower? I’m 74 with a few health issues starting lately. I’m thinking maybe so. I haven’t really done any tests in past 2 years. I usually set my ftp at what my Garmin tells me from outside rides. But now since I bought an e-bike I don’t think that will be so great from now on…

zwiftpower has me at 153 ftp I’ve had it set to 171 … I’m just basically wondering if I set it to 153 will I reap any benefits at all.

Zwiftpower shows your zFTP, what ZwiftHQ predicts you can sustain for 40-60mins.

FTP outside if Zwift is often estimated by taking 95% of your best 20mins effort and so will usually be higher.
This figure will be better to use for training, such as erg workouts.

Oh ok… Now I see the difference … Thanks