I prefer it when the box has a signature / sketch on it as opposed to the figure. It’s tricky to get a clean signature on a toy and most of the time the ink fades or bleeds into the vinyl.
In terms of value, I feel that back in the KR Forum days a signature on a toy felt like a much bigger deal – with lots of new artists entering the game and existing artists doing a lot more releases, more and more pieces are coming signed as standard.