People saying Gaga hasn't been artistic just because her latest album flopped are wrong. Gaga became more 'artistic' since The Fame Monster, The Fame was an EDM album in which she talked about partying and boys. It was a pop album, but afterwards she did more artistic stuff.
People saying Lana is staying in her own lane and doing the same
Ultraviolence and BTD are completely different records. So what if the GP perceives her music as boring sometimes? A lot of critically acclaimed/artistic music is not appealing to pop audiences.
I can't really vote, I'm not sure what people mean with artistic...is it a synonym for acclaim? For risk taking? For staying true to art (music not the bling)? The answers would be tie, Gaga, Lana mostly, respectively then.