jQuery Tools 1.2 was released over a year ago and by default still suggest jQuery 1.7.2, while jQuery UI is normally kept current with jQuery release (which does support the current jquery 1.9.1 out of the box)
jQuery UI has far more documentation, support, and the development is on going.
jQuery Tools = http://jquerytools.org/
jQuery UI = http://jqueryui.com/
Many of the modifications and fixes Mike has been applying to bring things up to speed are already done in jQuery UI. They also have a clear roadmap of what they're working on http://wiki.jqueryui.com/w/page/12138038/Roadmap