Reducing strength of (i-Bu)2AlH vs Lithium aluminum tri(t-butoxy)hydride

Hi Im trying to figure out which of the following is the stronger reducing agent.


(i-Bu)2AlH vs Lithium aluminum tri(t-butoxy)hydride


From my understanding, the Lithium aluminum tri(t-butoxy)hydride should be the stronger reducing reagent since it has a negative charge on the aluminum which would help push electron density onto the hydrogen. But on the lecture slides it says that Lithium aluminum tri(t-butoxy)hydride is a milder reducing agent. Can someone provide reasoning why that is the case. Thanks


