Battery life on the M1 is dramatically better. I regularly see 16 hours per charge on my Air.
Performance is also very good, but if you need a lot of graphics, the 16" Intel with DGPU is stronger.
Heat/fan noise is no contest. The M1 SOC runs cool, very cool. I love getting near-instantaneous responses on my Air and no fan noise. And even the 13" MBP M1 makes very little fan noise. Especially compared to the 16. My 16" would spin the fans all day long. Glad I got rid of it since the DGPU is not necessary for the tasks I do.
If you want a bigger more powerful system, you might want to wait a few weeks and see if they announce a 14" and 16" MBP based on the M1X/M2 SOC which will be a big step up from the M1.