Tommy

No such thing as "Lanthanated Pure"  lets get that out of the way.

Now.. I prefer Cerium (orange) for the type of work you describe, thin aluminum.

Cerium will carry as much current as thorium (red) or lanthanum (gold or black), about 1/3 more than Zirconium (brown) and twice as much current as pure tungsten (green).. But it degrades differently when overheated. The cerium electrodes will slowly round on the tip rather than growing those annoying nodules and spitting across the arc to ruin X-rays like thorium will.

I prefer Cerium over Lanthanum 1.5 or Lanthanum 2% because in my experience the arc tends to stay on the point of the electrode at low amps a little better with the cerium... The lanthanium electrodes I've used have always arced off the edge of the bevel when running low amps or tailing off at the end of a weld.

Having said all that... Different brands perform a bit differently and It costs very little (relatively) to buy a few boxes and run some quick trials to see what is the best thing you can get your hands on.