I lean AJB. He may have more competition for targets, but that may only mean that his targets are more productive. I believe Hurts to be much better than Dak along with being in an offense that runs like a well-oiled machine. Dak is turnover happy (continues to throw picks in training camp) and has a head coach that continuously underachieves. Rodgers was good enough to overcome it, Dak is not.
Lamb is not totally devoid of competition for targets. While Cooks/Gallup/Pollard are not on par with Philly's skill players, I wouldn't say Lamb "has no competition for targets" either.
It's close enough that the tie-breaker for me would be the QB and situation, which would put AJB ahead by a smidge in that regard.