Fujifilm X-T3 has a 26.0MP APS-C (23.5 x 15.6 mm ) sized X-Trans CMOS 4 sensor and features X-Processor 4 processor. On the other hand, Fujifilm X-T2 has a 24.0MP APS-C (23.6 x 15.6 mm ) sized CMOS X-TRANS III sensor and features X-Processor Pro2 processor.
Another similarity between these two cameras is that both Fujifilm X-T2 and Fujifilm X-T3 sensors lack anti-alias (Low-Pass) filters. Removing anti-alias filter increases the sharpness and level of detail but at the same time, it increases the chance of moire occurring in certain scenes.
Below you can see the X-T3 and X-T2 sensor size comparison.
Fujifilm X-T3 and Fujifilm X-T2 have almost the same sensor size so none of them has any significant advantage over other in providing control over depth of field when used with same focal length and aperture.