You are one step ahead of me, i never managed to build the Qt version myself :-P. Although i didn't try much, i rarely use Macs these days and mostly wanted to see if some minor issue i had with the Carbon build would go away with the Qt backend (the Cocoa backend was basically unusable at the time, although i think today it would work ok).
TBH i'm not sure if it would be Qt5 or the data access components as personally i don't use either :-P. I use Lazarus to make tools mainly for game development (and mainly for 3D stuff) so i don't use the database features at all. Also i tend to use the Gtk2 backend on Linux, mostly because it is the default but also because it tends to fit better the minimalistic window managers i am using (mainly window maker).
TBH i'm not sure if it would be Qt5 or the data access components as personally i don't use either :-P. I use Lazarus to make tools mainly for game development (and mainly for 3D stuff) so i don't use the database features at all. Also i tend to use the Gtk2 backend on Linux, mostly because it is the default but also because it tends to fit better the minimalistic window managers i am using (mainly window maker).