Dilruba/Esraj
The easiest way into bowed Indian music, and the reason is the neck.
Both instruments are fretted like a sitar, so the left hand does something familiar and you are not hunting for pitch on a bare fingerboard the way you are on a sarangi. The bow takes the practice, as with any bowed instrument, but the learning curve is human.
Dilruba or esraj? Regional and constructional cousins, dilruba associated with the north and Punjab, esraj with Bengal. Both have a fretted neck, a skin belly and sympathetic strings that ring underneath the bowed note. If you are learning within a tradition, follow your teacher. If not, either will serve.
Where they are used. Sikh kirtan and gurmat sangeet, Bengali devotional and classical music, film scoring, and increasingly by string players from other traditions who want that voice-like sustain.
And the taus? The taus is the larger, older ancestor of the dilruba, carved into a peacock and considerably deeper. If the tradition matters to you more than the portability, look there.