What are the biggest differences/advantages between the two grips? I feel like underhand would work the lats more.

sorta like pullup vs chin up

to some degree

bicep involvement is different

more so just secondary muscles being targeted

just find the one that works the best for you !. I do dbl underhand

Basically

I felt like it was harder to squeeze Lats with overhand and currently doing underhand with short, curved bar, for like 3 months. Never felt more confident with rows.

this is what i just started doing. im using my curl bar. i feel like its working more back/lat than tricep like it was with a regular barbell

Some of these responses are ridiculous.

There are a lot of muscles in your back. Each works different primary muscles if you're doing it right. Another thing affecting which muscles get targeted and how much is how far you bend over

I do both.

how wide your grip is also

the difference between supination and pronation is mostly in the forearm muscles involved, and the orientation and recruitment of biceps brachii fibers, but also in the inherent stability of the shoulder joint. the glenohumeral joint tends to be more stable in an externally rotated position relative to an internally rotated one (why upright rows are iffy)

It literally makes little difference do whichever is most comforable