Both are Statesmans, one is a Deville and the other is a Caprice. The SL/E was a "budget" version of the Caprice meant to catch buyers who wanted more than a Deville but not the cost of a Caprice. It isn't badged as a Caprice though, just shared the model coding - that was always how GMH did such things: HQ SS sedan was a V8 Belmont, HQ GTS sedan was a V8 Kingswood, XU-1 was a GTR, A9X was an SS, Sandman was a Belmont or Kingswood etc. Even many UC Toranas were option packages on a Sunbird. The other HZ that was "back-optioned" like the SL/E was a HZ Kingswood sedan or wagon, they shared the same model coding as a Kingswood SL but had lots of stuff stripped out to minimise cost (option package A9K). I can't remember the specifics, but I think Caprice had leather trim as standard with velour as a delete option. The SL/E got that velour trim.
I just found my HZ Statesman stuff. Deville was $10635 at release in November 1977, Caprice was $15504. In June 1979 SL/E was $14560, so allowing for some price rises it was over $1000 cheaper than a Caprice. You couldn't order a Caprice after August 1979, Deville was available until April 1980.