Pencil is pretty good I just started using it a few months ago and am impressed it's an open source project, however it's been 2 years since the last commit...
I use Adobe XD.
Compared to Sketch, it doesn't have as many plugins.
Compared to Origami, the animation controls are not as fine.
Compared to PaintCode, it can only export styles.
However, it's free, plus there are lots of templates out there, plus there are auto animate and integration with other Adobe tools. It's not the best at anything, but is good enough at everything for my needs.
Figma for higher-fidelity discussions (colors, spacing, icons, etc.)