They're consumer models, and the ones most likely to be affected by Lenovo's malware shenanigans. Most "PC" OEMs tend to build their business lines better than their consumer lines, and Lenovo's no exception. The Thinkpad line also has a reputation of being friendlier to non-Windows operating systems in general (they're the most-recommended for OpenBSD, for example), while the Ideapad line very much does not.
"Why get a Developer Edition?"
Because they're designed with Linux compatibility in mind, from what I understand.
Obviously they are not carved from a solid block of magnesium alloy, like ThinkPads used to be.
And the ThinkPad units didn't have Superfish or the Win10-only-SSD BIOS lock.
"Developer Edition" is Dell's corporatespeak for "we made sure this works with linux".
So you're probably looking at a 10.6" netbook.
I was speaking from past experience and my frustration at the poor build quality, poor management, and all the creepy stuff Lenovo has done to laptops in the Ideapad line (Superfish, Win10-only SSD (which they recently backed down from) etc.)
Beyond me, others would tell you that IdeaPad is Lenovo's consumer laptop line, and as such it sees less quality put into it.
> Why get a Developer Edition?
Because those units are built for Linux compatibility, while non–Developer Edition units are hit-and-miss.