You'd be better off comparing Christmas to Gary Neal, as a guy who went to Europe for a bit after failing to catch on with a team in the NBA. Since he has had a few extra years to mature, I would guess that he has a better chance of contributing than Joseph. Wages of Win, whose work I love, suggests Christmas has the ability to be a hidden gem, based on his performance in Europe.
I like being willing to gamble with a guy like Christmas over the sort of declining "proven veteran" available for the minimum who might be considered for a third-string wing position on the bench.
One thing that gives Christmas the edge over Joseph is that his contract contains a partial guarantee.