Exactly, think of GarageBand as Logic Light (or maybe "Logic Very Light").
The main limitation, in my opinion, is that GarageBand doesn't have a Mixer, and the routing is kind of mysteriously happen behind the Smart Controls. The funny thing is that if you use the (free) Logic Remote app on iOS as with GarageBand as a control surface, then voila, you have a mixer like in Logic Pro.
Apple makes it very easy if you decide to upgrade from GarageBand to Logic. You can turn off the advanced features so you are not overwhelmed with too much new stuff. It even gives you the familiar wood panels on the side and the same buttons on the Track Header.
Hope that helps
EdgarRothermich - LogicProGEM.com
(Author of the "Graphically Enhanced Manuals")
http://DingDingMusic.com/Manuals/
'I may receive some form of compensation, financial or otherwise, from my recommendation or link.'