It comes down to tradeoffs...
If they go it alone, they have to dilute to raise funds, but ultimately keep 100% of earnings. This path causes a drag on the share price until FDA approval.
If they partner to generate funds, that has an immediate positive affect on the share price, but revenue sharing will reduce the earnings for Anavex.
I think as investors, most would prefer the path that supports short-term share price. The long term will take care of itself.