I want to build a small trainer kit. Which is better - the Goldberg Eaglet or the Sig Seniorita?

How about a Sig LT-25? About the size of the Seniorita but a lot easier to build and comes with ailerons-

I had the Eaglet when I was in high school, it was my first plane. I have the Eagle now. Both planes are very good. The Kadets are supposed to be just as good, and were indeed my other choice.

Either way, I don't think you'll go wrong.

I haven't had a Kadet, but I just finished building a Sig 4 Star and the build was a great experience..

I love my Seniorita and have taught many others to fly with it as well.

Both planes are good trainers. The Seniorita uses traditional stick construction and is a very labor intensive project with some finicky details in the cabin and wing center area. In other words, you will spend a long time building it. To get into the air quicker get a modern laser-cut balsa kit (not lite-ply) such as the Sig LT-40 or LT-25. Easy to build and fine flyers.