convex vs concave resistor arrays
Convex have five sided terminations for easier or better soldering.  The space between terminations is better with convex (generally 0.1mm).  Visual checking of soldering is easier with convex, as the solder is not sucked in and hidden from view.  Convex is also supposed to self align better, due to the terminators allowing side force from the solder.

I don't know that there are any advantages of concave arrays.  The majority seem to be convex these days.  I see some references to concave self centering, so maybe they both do.