Asides from the fact that the former has five more letters and one more space, I perceive no difference between the two and can't think of any context in which one could not appropriately replace the other. At best, if being used to introduce something, the grammar would have to change a little, e.g. Let's get started on building this table. vs. Let's start building this table. (although re-reading that, I think that I would default to the latter, for the sole reason that it's a bit more straightforward of a sentence). – Samuel Lijin Jun 5 at 0:51