这两种表达方式都对
基本上没有实质上的差别.
短语 a lot of work to do
可以理解为
a lot of work (for us/him/her ...) to do
的变体.
其他表达方式有
there is a lot of work ahead of us
much is left to do
much is left to be done
much is yet to be done
there is much to be completed
much work remains ahead
we ain't done yet; not by any stretch of imagination（口语）
等等,等等.
我是加拿大人,前英语老师.