I couldn't find an exact exposure time for the Hubble image, the press release by the ESA has this quote though: "This deep field, taken by Webb’s Near-Infrared Camera (NIRCam), is a composite made from images at different wavelengths, totaling 12.5 hours – achieving depths at infrared wavelengths beyond the Hubble Space Telescope’s deepest fields, which took weeks." [1] There is also another comment further down this thread stating Hubble was 140 hours. [2]

[1] https://www.esa.int/ESA_Multimedia/Images/2022/07/Webb_s_fir... [2] https://news.ycombinator.com/item?id=32063214