Wouldn't Inkpad be in a different category as it is a vector drawing app?
Pages is not vector based, so you souldn't compare it Inkpad. Each excels in it's category.
They were different categories at first, but in looking for a general sketching app, we sort of drifted from raster apps to settling on Adobe Ideas, which, while technically a vector app, behaves like a basic raster App. Can't make selections on the object level, has a raster eraser instead of delete, moves & scales by layer, etc... we used it for about a year til we started playing around with vector apps, but found most heavily burdened by busy UIs and clunky commands. Inkpad seems to have the best balance between a fast, clean, minimalist UI and powerful drawing tools.
+ being able to import/export .pngs with trans backgrounds AND .svg to/from CAD (& illustrator) via dropbox makes everything from sketching comps to tweaking actual design geometry wundebar.
I should be getting paid, I'd make a pretty good shill.