Could anyone tell me the main differences between dry bath (using Peltier or resistance) and water bath temperature system, related to the stability of the temperatura (37 celsius)?
Depends on the details. In general a water bath with a sufficient reservoir could dampen temperature changes better but can't be turned up or down as quickly It can have at the site footprints much better than a dry load although the support hardware will likely be generally larger the actual thermal interface is much much smaller for peltier cooling or air cooling with a static heat sink. There is less advantage in heating as heating elements don't have to be large and are inherently 100% efficient.